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Sample records for perpendicular uniaxial anisotropy

  1. Freezing field dependence of the exchange bias in uniaxial FeF sub 2 -CoPt heterosystems with perpendicular anisotropy

    CERN Document Server

    Kagerer, B; Kleemann, W

    2000-01-01

    The exchange bias effect is measured for the first time in FeF sub 2 -CoPt heterosystems with perpendicular anisotropy. The exchange field exhibits a strong dependence on the axial freezing field. This behavior is explained in terms of the microscopic spin structure at the interface, which is established on cooling to below T sub N. We calculate the dependence of the spin structure on the freezing field within the framework of an Ising model. It takes into account the Zeeman energy as well as an antiferromagnetic exchange coupling between the adjacent layers at the interface.

  2. Switching the uniaxial magnetic anisotropy by ion irradiation induced compensation

    Science.gov (United States)

    Yuan, Ye; Amarouche, Teyri; Xu, Chi; Rushforth, Andrew; Böttger, Roman; Edmonds, Kevin; Campion, Richard; Gallagher, Bryan; Helm, Manfred; Jürgen von Bardeleben, Hans; Zhou, Shengqiang

    2018-04-01

    In the present work, the uniaxial magnetic anisotropy of GaMnAsP is modified by helium ion irradiation. According to the micro-magnetic parameters, e.g. resonance fields and anisotropy constants deduced from ferromagnetic resonance measurements, a rotation of the magnetic easy axis from out-of-plane [0 0 1] to in-plane [1 0 0] direction is achieved. From the application point of view, our work presents a novel avenue in modifying the uniaxial magnetic anisotropy in GaMnAsP with the possibility of lateral patterning by using lithography or focused ion beam.

  3. Effect of soft underlayer magnetic anisotropy on perpendicular recording process

    International Nuclear Information System (INIS)

    Lim, C.K.; Kim, E.S.; Yoon, S.Y.; Kong, S.H.; Lee, H.S.; Oh, H.S.; Kim, Y.S.

    2007-01-01

    The presence of the soft magnetic underlayer (SUL) in perpendicular magnetic recording (PMR) media is essential for the application. It is commonly understood that the SUL provides the return flux path and enhances the writing field by enhancing the recording field from the write pole. However, SUL increases the magnetic noise during the read back process due to magnetic domain walls in the SUL. Hence, it is common to grow SUL with large uniaxial or unidirectional magnetic anisotropy field (H k ) to reduce domain wall noise. In this paper, we explore the effect of increasing SUL H k on the recording process. We studied this effect by using the finite element micromagnetic simulation. Our simulation results show that the contribution of SUL to the writing field amplitude is reduced with increasing H k . This reduction in magnetic field from high H k SUL actually improves the recording performance due to the better field gradient at SUL. The simulation results are qualitatively consistent with the actual experimental data obtained from the Guzik measurement

  4. Origin of perpendicular magnetic anisotropy in Co/Ni multilayers

    Science.gov (United States)

    Arora, M.; Hübner, R.; Suess, D.; Heinrich, B.; Girt, E.

    2017-07-01

    We studied the variation in perpendicular magnetic anisotropy of (111) textured Au /N ×[Co /Ni ]/Au films as a function of the number of bilayer repeats N . The ferromagnetic resonance and superconducting quantum interference device magnetometer measurements show that the perpendicular magnetic anisotropy of Co/Ni multilayers first increases with N for N ≤10 and then moderately decreases for N >10 . The model we propose reveals that the decrease of the anisotropy for N reduction in the magnetoelastic and magnetocrystalline anisotropies. A moderate decrease in the perpendicular magnetic anisotropy for N >10 is due to the reduction in the magnetocrystalline and the surface anisotropies. To calculate the contribution of magnetoelastic anisotropy in the Co/Ni multilayers, in-plane and out-of-plane x-ray diffraction measurements are performed to determine the spacing between Co/Ni (111) and (220) planes. The magnetocrystalline bulk anisotropy is estimated from the difference in the perpendicular and parallel g factors of Co/Ni multilayers that are measured using the in-plane and out-of-plane ferromagnetic resonance measurements. Transmission electron microscopy has been used to estimate the multilayer film roughness. These values are used to calculate the roughness-induced surface and magnetocrystalline anisotropy coefficients as a function of N .

  5. Perpendicular magnetic anisotropy and the magnetization process in CoFeB/Pd multilayer films

    International Nuclear Information System (INIS)

    Ngo, Duc-The; Tran, Quang-Hung; Møhave, Kristian; Quach, Duy-Truong; Phan, The-Long; Kim, Dong-Hyun

    2014-01-01

    The perpendicular magnetic anisotropy (PMA) and dynamic magnetization-reversal process in [CoFeB t nm/Pd 1.0 nm] n (t = 0.4, 0.6, 0.8, 1.0 and 1.2 nm; n = 2 − 20) multilayer films have been studied by means of magnetic hysteresis and Kerr effect measurements. Strong and controllable PMA with an effective uniaxial anisotropy up to 7.7 × 10 6  Jm −3 and a saturation magnetization as low as 200 emu cm −3 are achieved. The surface/interfacial anisotropy of the CoFeB/Pd interfaces—the main contribution to the PMA—is separated from the effective uniaxial anisotropy of the films and appears to increase with the number of CoFeB/Pd bilayers. Observation of the magnetic domains during a magnetization-reversal process, using polar magneto-optical Kerr microscopy, reveals the detailed behavior of the nucleation and displacement of the domain walls. (paper)

  6. NANO-MULTILAYERS WITH HIGH PERPENDICULAR ANISOTROPY FOR MAGNETIC RECORDING

    Institute of Scientific and Technical Information of China (English)

    T. Yang; B.H. Li; K. Kang; T. Suzuki

    2003-01-01

    (FePt/Ag)n nano-multilayers were deposited on MgO (100) single crystal with laser ablation and then subjected to annealing. FePt L1o grains with (001) texture and thus a large perpendicular magnetic anisotropy constant Ku of the order of 106J/m3 were formed. A thick Ag layer is found to be favorable for decreasing the dispersion of the easy axis for magnetization. The measurement of time decay of magnetization gave rise to a small activation volume of the order of 10-25 m3, showing the promising of being the recording medium for future high density perpendicular recording.

  7. Self-assembly of heterogeneous supramolecular structures with uniaxial anisotropy.

    Science.gov (United States)

    Ruiz-Osés, M; Gonzalez-Lakunza, N; Silanes, I; Gourdon, A; Arnau, A; Ortega, J E

    2006-12-28

    Uniaxial anisotropy in two-dimensional self-assembled supramolecular structures is achieved by the coadsorption of two different linear molecules with complementary amine and imide functionalization. The two-dimensional monolayer is defined by a one-dimensional stack of binary chains, which can be forced to line up along steps in vicinal surfaces. The competing driving forces in the self-organization process are discussed in light of the structures observed during single molecule adsorption and coadsorption on flat and vicinal surfaces and the corresponding theoretical calculations.

  8. Nanoconstriction spin-Hall oscillator with perpendicular magnetic anisotropy

    Science.gov (United States)

    Divinskiy, B.; Demidov, V. E.; Kozhanov, A.; Rinkevich, A. B.; Demokritov, S. O.; Urazhdin, S.

    2017-07-01

    We experimentally study spin-Hall nano-oscillators based on [Co/Ni] multilayers with perpendicular magnetic anisotropy. We show that these devices exhibit single-frequency auto-oscillations at current densities comparable to those for in-plane magnetized oscillators. The demonstrated oscillators exhibit large magnetization precession amplitudes, and their oscillation frequency is highly tunable by the electric current. These features make them promising for applications in high-speed integrated microwave circuits.

  9. Interfacial tuning of perpendicular magnetic anisotropy and spin magnetic moment in CoFe/Pd multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Ngo, D.-T., E-mail: ndthe82@gmail.com [Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 117576 (Singapore); Meng, Z.L. [Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 117576 (Singapore); Tahmasebi, T. [Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 117576 (Singapore); Data Storage Institute, A-STAR (Agency for Science Technology and Research), 5 Engineering Drive 1, Singapore 117608 (Singapore); Yu, X. [Singapore Synchrotron Light Source, National University of Singapore, 5 Research Link, Singapore 117603 (Singapore); Thoeng, E. [Singapore Synchrotron Light Source, National University of Singapore, 5 Research Link, Singapore 117603 (Singapore); Department of Physics, National University of Singapore, Singapore 117542 (Singapore); Yeo, L.H. [Department of Physics, National University of Singapore, Singapore 117542 (Singapore); Rusydi, A., E-mail: phyandri@nus.edu.sg [Singapore Synchrotron Light Source, National University of Singapore, 5 Research Link, Singapore 117603 (Singapore); Department of Physics, National University of Singapore, Singapore 117542 (Singapore); Han, G.C [Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 117576 (Singapore); Teo, K.-L., E-mail: eleteokl@nus.edu.sg [Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 117576 (Singapore)

    2014-01-15

    We report on a strong perpendicular magnetic anisotropy in [CoFe 0.4 nm/Pd t]{sub 6} (t=1.0–2.0 nm) multilayers fabricated by DC sputtering in an ultrahigh vacuum chamber. Saturation magnetization, M{sub s}, and uniaxial anisotropy, K{sub u}, of the multilayers decrease with increasing the spacing thickness; with a M{sub s} of 155 emu/cc and a K{sub u} of 1.14×10{sup 5} J/m{sup 3} at a spacing thickness of t=2 nm. X-ray absorption spectroscopy and X-ray magnetic circular dichroism measurements reveal that spin and orbital magnetic moments of Co and Fe in CoFe film decrease as a function of Pd thickness, indicating the major contribution of surface/interfacial magnetism to the magnetic properties of the film. - Highlights: • Strong perpendicular magnetic anisotropy essentially contributed by interfacial anisotropy. • Controllably magnetic properties with low M{sub s}, high K{sub u}, high P. • Interfacial magnetic moments modified by CoFe/Pd interfaces with strong spin–orbit coupling. • Narrow Bloch walls with Néel caps. • Superior magnetic characteristics for spin-torque applications.

  10. Uniaxial anisotropy in magnetite thin film-Magnetization studies

    International Nuclear Information System (INIS)

    Wiechec, A.; Korecki, J.; Handke, B.; Kakol, Z.; Owoc, D.; Antolak, D.A.; Kozlowski, A.

    2006-01-01

    Magnetization and electrical resistivity measurements have been performed on a stoichiometric single crystalline magnetite Fe 3 O 4 thin film (thickness of ca. 500 nm) MBE deposited on MgO (1 0 0) substrate. The aim of these studies was to check the influence of preparation method and sample form (bulk vs. thin film) on magnetic anisotropy properties in magnetite. The film magnetization along versus applied magnetic field has been determined both in the direction parallel and perpendicular to the film surface, and at temperatures above and below the Verwey transition. We have found, in agreement with published results, that the in-plane field of 10 kOe was not sufficient to saturate the sample. This can be understood if some additional factor, on top of the bulk magnetocrystalline anisotropy, is taken into account

  11. Tunnel Junction with Perpendicular Magnetic Anisotropy: Status and Challenges

    Directory of Open Access Journals (Sweden)

    Mengxing Wang

    2015-08-01

    Full Text Available Magnetic tunnel junction (MTJ, which arises from emerging spintronics, has the potential to become the basic component of novel memory, logic circuits, and other applications. Particularly since the first demonstration of current induced magnetization switching in MTJ, spin transfer torque magnetic random access memory (STT-MRAM has sparked a huge interest thanks to its non-volatility, fast access speed, and infinite endurance. However, along with the advanced nodes scaling, MTJ with in-plane magnetic anisotropy suffers from modest thermal stability, high power consumption, and manufactural challenges. To address these concerns, focus of research has converted to the preferable perpendicular magnetic anisotropy (PMA based MTJ, whereas a number of conditions still have to be met before its practical application. This paper overviews the principles of PMA and STT, where relevant issues are preliminarily discussed. Centering on the interfacial PMA in CoFeB/MgO system, we present the fundamentals and latest progress in the engineering, material, and structural points of view. The last part illustrates potential investigations and applications with regard to MTJ with interfacial PMA.

  12. Tailoring perpendicular magnetic anisotropy with graphene oxide membranes

    KAUST Repository

    Ning, Keyu; Liu, Houfang; Li, Linsen; Li, Huanglong; Feng, Jiafeng; Yang, Baishun; Liu, Xiao; Li, Yuxing; Chen, Yanhui; Wei, Hongxiang; Han, Xiufeng; Mao, Shengcheng; Zhang, Xixiang; Yang, Yi; Ren, Tian-ling

    2017-01-01

    Graphene oxide (GO) membranes have been widely explored for their excellent physical and chemical properties, and abundant functional groups. In this work, we report the improvement of the perpendicular magnetic anisotropy (PMA) of CoFeB thin films by applying a coating of GO membranes. We observe that the PMA of the CoFeB/MgAl–O stacks is strongly enhanced by the coating of GO membranes and even reaches 0.6 mJ m−2 at room temperature after an annealing process. The critical thickness of the membrane-coated CoFeB for switching the magnetization from the out-of-plane to the in-plane axis exceeds 1.6 nm. First-principle calculations are performed to investigate the contribution of the GO membranes to the magnetic anisotropy energy (MAE). Due to changes in the hybridization of 3d orbitals, varying the location of the C atomic layer with Co changes the contribution of the Co–C stacks to PMA. Thus, the large PMA achieved with GO membranes can be attributed to the orbital hybridization of the C and O atoms with the Co orbitals. These results provide a comprehensive understanding of the PMA and point towards opportunities to achieve multifunctional graphene-composite spintronic devices.

  13. Tailoring perpendicular magnetic anisotropy with graphene oxide membranes

    KAUST Repository

    Ning, Keyu

    2017-11-15

    Graphene oxide (GO) membranes have been widely explored for their excellent physical and chemical properties, and abundant functional groups. In this work, we report the improvement of the perpendicular magnetic anisotropy (PMA) of CoFeB thin films by applying a coating of GO membranes. We observe that the PMA of the CoFeB/MgAl–O stacks is strongly enhanced by the coating of GO membranes and even reaches 0.6 mJ m−2 at room temperature after an annealing process. The critical thickness of the membrane-coated CoFeB for switching the magnetization from the out-of-plane to the in-plane axis exceeds 1.6 nm. First-principle calculations are performed to investigate the contribution of the GO membranes to the magnetic anisotropy energy (MAE). Due to changes in the hybridization of 3d orbitals, varying the location of the C atomic layer with Co changes the contribution of the Co–C stacks to PMA. Thus, the large PMA achieved with GO membranes can be attributed to the orbital hybridization of the C and O atoms with the Co orbitals. These results provide a comprehensive understanding of the PMA and point towards opportunities to achieve multifunctional graphene-composite spintronic devices.

  14. Quantum Monte Carlo simulation for S=1 Heisenberg model with uniaxial anisotropy

    International Nuclear Information System (INIS)

    Tsukamoto, Mitsuaki; Batista, Cristian; Kawashima, Naoki

    2007-01-01

    We perform quantum Monte Carlo simulations for S=1 Heisenberg model with an uniaxial anisotropy. The system exhibits a phase transition as we vary the anisotropy and a long range order appears at a finite temperature when the exchange interaction J is comparable to the uniaxial anisotropy D. We investigate quantum critical phenomena of this model and obtain the line of the phase transition which approaches a power-law with logarithmic corrections at low temperature. We derive the form of logarithmic corrections analytically and compare it to our simulation results

  15. Achieving perpendicular anisotropy in half-metallic Heusler alloys for spin device applications

    Science.gov (United States)

    Munira, Kamaram; Romero, Jonathon; Butler, William H.

    2014-05-01

    Various full Heusler alloys are interfaced with MgO and the magnetic properties of the Heusler-MgO junctions are studied. Next to MgO, the cubic Heusler system distorts to a tetragonal one, thereby inducing an anisotropy. The half-metallicity and nature of anisotropy (in-plane or perpendicular) in the Heusler-MgO system is governed mostly by the interface Heusler layers. There is a trend that Mn-O bonding near the MgO-Heusler junction results in perpendicular anisotropy. The ability to remain half-metallic and have perpendicular anisotropy makes some of these alloys potential candidates as free-layers in Spin Transfer Torque Random Access Memory (STT-RAM) devices, particularly, Cr2MnAs-MgO system with MnAs interface layers and Co2MnSi-MgO system with Mn2 interface layers.

  16. Angular dependence of magnetization reversal in epitaxial chromium telluride thin films with perpendicular magnetic anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Pramanik, Tanmoy, E-mail: pramanik.tanmoy@utexas.edu; Roy, Anupam, E-mail: anupam@austin.utexas.edu; Dey, Rik, E-mail: rikdey@utexas.edu; Rai, Amritesh; Guchhait, Samaresh; Movva, Hema C.P.; Hsieh, Cheng-Chih; Banerjee, Sanjay K.

    2017-09-01

    Highlights: • Perpendicular magnetic anisotropy in epitaxial Cr{sub 2}Te{sub 3} has been investigated. • Presence of a relatively strong second order anisotropy contribution is observed. • Magnetization reversal is explained quantitatively using a 1D defect model. • Relative roles of nucleation and pinning in magnetization reversal are discussed. • Domain structures and switching process are visualized by micromagnetic simulation. - Abstract: We investigate magnetic anisotropy and magnetization reversal mechanism in chromium telluride thin films grown by molecular beam epitaxy. We report existence of strong perpendicular magnetic anisotropy in these thin films, along with a relatively strong second order anisotropy contribution. The angular variation of the switching field observed from the magnetoresistance measurement is explained quantitatively using a one-dimensional defect model. The model reveals the relative roles of nucleation and pinning in the magnetization reversal, depending on the applied field orientation. Micromagnetic simulations are performed to visualize the domain structure and switching process.

  17. Origin of perpendicular magnetic anisotropy of SmCo5 thin films with Cu underlayer

    International Nuclear Information System (INIS)

    Sayama, Junichi; Mizutani, Kazuki; Asahi, Toru; Ariake, Jun; Ouchi, Kazuhiro; Osaka, Tetsuya

    2006-01-01

    Effects of the Cu underlayer thickness and the addition of Cu to a Sm-Co layer on magnetic properties and microstructure of SmCo 5 thin films exhibiting perpendicular magnetic anisotropy were studied. The origin of the perpendicular magnetic anisotropy was discussed from these experimental results. A thick Cu underlayer of more than 100 nm brought about high perpendicular magnetic anisotropy leading to the squareness ratio equal to unity. The Cu addition enhanced the perpendicular magnetic anisotropy and reduced the Cu underlayer thickness required to obtain the squareness ratio of unity. X-ray diffractometry showed that the crystalline orientation of the Sm-Co layer did not correlate with that of the Cu underlayer. Auger electron spectroscopy revealed that Cu atoms were diffused up to the Sm-Co layer from the Cu underlayer. From the results, Cu atoms existing in the Sm-Co layer were suggested to be strongly related with an appearance of the perpendicular magnetic anisotropy by introducing the Cu underlayer

  18. Nanocrystalline iron nitride films with perpendicular magnetic anisotropy

    International Nuclear Information System (INIS)

    Gupta, Ajay; Dubey, Ranu; Leitenberger, W.; Pietsch, U.

    2008-01-01

    Nanocrystalline α-iron nitride films have been prepared using reactive ion-beam sputtering. Films develop significant perpendicualr magnetic anisotropy (PMA) with increasing thickness. A comparison of x-ray diffraction patterns taken with scattering vectors in the film plane and out of the film plane provides a clear evidence for development of compressive strain in the film plane with thickness. Thermal annealing results in relaxation of the strain, which correlates very well with the relaxation of PMA. This suggests that the observed PMA is a consequence of the breaking of the symmetry of the crystal structure due to the compressive strain

  19. Direct Observation of Magnetocrystalline Anisotropy Tuning Magnetization Configurations in Uniaxial Magnetic Nanomaterials

    KAUST Repository

    Zhu, Shimeng; Fu, Jiecai; Li, Hongli; Zhu, Liu; Hu, Yang; Xia, Weixing; Zhang, Xixiang; Peng, Yong; Zhang, Junli

    2018-01-01

    Discovering the effect of magnetic anisotropy on the magnetization configurations of magnetic nanomaterials is essential and significant for not only enriching the fundamental knowledge of magnetics but also facilitating the designs of desired magnetic nanostructures for diverse technological applications, such as data storage devices, spintronic devices, and magnetic nanosensors. Herein, we present a direct observation of magnetocrystalline anisotropy tuning magnetization configurations in uniaxial magnetic nanomaterials with hexagonal structure by means of three modeled samples. The magnetic configuration in polycrystalline BaFe12O19 nanoslice is a curling structure, revealing that the effect of magnetocrystalline anisotropy in uniaxial magnetic nanomaterials can be broken by forming an amorphous structure or polycrystalline structure with tiny grains. Both single crystalline BaFe12O19 nanoslice and individual particles of single-particle-chain BaFe12O19 nanowire appear in a single domain state, revealing a dominant role of magnetocrystalline anisotropy in the magnetization configuration of uniaxial magnetic nanomaterials. These observations are further verified by micromagnetic computational simulations.

  20. Direct Observation of Magnetocrystalline Anisotropy Tuning Magnetization Configurations in Uniaxial Magnetic Nanomaterials

    KAUST Repository

    Zhu, Shimeng

    2018-03-20

    Discovering the effect of magnetic anisotropy on the magnetization configurations of magnetic nanomaterials is essential and significant for not only enriching the fundamental knowledge of magnetics but also facilitating the designs of desired magnetic nanostructures for diverse technological applications, such as data storage devices, spintronic devices, and magnetic nanosensors. Herein, we present a direct observation of magnetocrystalline anisotropy tuning magnetization configurations in uniaxial magnetic nanomaterials with hexagonal structure by means of three modeled samples. The magnetic configuration in polycrystalline BaFe12O19 nanoslice is a curling structure, revealing that the effect of magnetocrystalline anisotropy in uniaxial magnetic nanomaterials can be broken by forming an amorphous structure or polycrystalline structure with tiny grains. Both single crystalline BaFe12O19 nanoslice and individual particles of single-particle-chain BaFe12O19 nanowire appear in a single domain state, revealing a dominant role of magnetocrystalline anisotropy in the magnetization configuration of uniaxial magnetic nanomaterials. These observations are further verified by micromagnetic computational simulations.

  1. Symmetry mismatch-driven perpendicular magnetic anisotropy for perovskite/brownmillerite heterostructures.

    Science.gov (United States)

    Zhang, Jing; Zhong, Zhicheng; Guan, Xiangxiang; Shen, Xi; Zhang, Jine; Han, Furong; Zhang, Hui; Zhang, Hongrui; Yan, Xi; Zhang, Qinghua; Gu, Lin; Hu, Fengxia; Yu, Richeng; Shen, Baogen; Sun, Jirong

    2018-05-15

    Grouping different transition metal oxides together by interface engineering is an important route toward emergent phenomenon. While most of the previous works focused on the interface effects in perovskite/perovskite heterostructures, here we reported on a symmetry mismatch-driven spin reorientation toward perpendicular magnetic anisotropy in perovskite/brownmillerite heterostructures, which is scarcely seen in tensile perovskite/perovskite heterostructures. We show that alternately stacking perovskite La 2/3 Sr 1/3 MnO 3 and brownmillerite LaCoO 2.5 causes a strong interface reconstruction due to symmetry discontinuity at interface: neighboring MnO 6 octahedra and CoO 4 tetrahedra at the perovskite/brownmillerite interface cooperatively relax in a manner that is unavailable for perovskite/perovskite interface, leading to distinct orbital reconstructions and thus the perpendicular magnetic anisotropy. Moreover, the perpendicular magnetic anisotropy is robust, with an anisotropy constant two orders of magnitude greater than the in-plane anisotropy of the perovskite/perovskite interface. The present work demonstrates the great potential of symmetry engineering in designing artificial materials on demand.

  2. CeCo5 thin films with perpendicular anisotropy grown by molecular beam epitaxy

    Science.gov (United States)

    Sharma, S.; Hildebrandt, E.; Major, M.; Komissinskiy, P.; Radulov, I.; Alff, L.

    2018-04-01

    Buffer-free, highly textured (0 0 1) oriented CeCo5 thin films showing perpendicular magnetic anisotropy were synthesized on (0 0 1) Al2O3 substrates by molecular beam epitaxy. Ce exists in a mixture of Ce3+ and Ce4+ valence states as shown by X-ray photoelectron spectroscopy. The first anisotropy constant, K1, as measured by torque magnetometry was 0.82 MJ/m3 (8.2 ×106erg /cm3) . A maximum coercivity of 5.16 kOe with a negative temperature coefficient of -0.304%K-1 and a magnetization of 527.30 emu/cm3 was measured perpendicular to the film plane at 5 K. In addition, a large anisotropy of the magnetic moment of 15.5% was observed. These magnetic parameters make CeCo5 a potential candidate material for spintronic and magnetic recording applications.

  3. On the limits of uniaxial magnetic anisotropy tuning by a ripple surface pattern

    Energy Technology Data Exchange (ETDEWEB)

    Arranz, Miguel A. [Facultad de Ciencias Químicas, Universidad de Castilla-La Mancha, Avda. Camilo J. Cela 10, 13071 Ciudad Real (Spain); Colino, Jose M., E-mail: josemiguel.colino@uclm.es [Instituto de Nanociencia, Nanotecnología y Materiales Moleculares, Universidad de Castilla-La Mancha, Campus de la Fábrica de Armas, 45071 Toledo (Spain); Palomares, Francisco J. [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas, c/ Sor Juana Inés de la Cruz 3, 28049 Madrid (Spain)

    2014-05-14

    Ion beam patterning of a nanoscale ripple surface has emerged as a versatile method of imprinting uniaxial magnetic anisotropy (UMA) on a desired in-plane direction in magnetic films. In the case of ripple patterned thick films, dipolar interactions around the top and/or bottom interfaces are generally assumed to drive this effect following Schlömann's calculations for demagnetizing fields of an ideally sinusoidal surface [E. Schlömann, J. Appl. Phys. 41, 1617 (1970)]. We have explored the validity of his predictions and the limits of ion beam sputtering to induce UMA in a ferromagnetic system where other relevant sources of magnetic anisotropy are neglected: ripple films not displaying any evidence of volume uniaxial anisotropy and where magnetocrystalline contributions average out in a fine grain polycrystal structure. To this purpose, the surface of 100 nm cobalt films grown on flat substrates has been irradiated at fixed ion energy, fixed ion fluency but different ion densities to make the ripple pattern at the top surface with wavelength Λ and selected, large amplitudes (ω) up to 20 nm so that stray dipolar fields are enhanced, while the residual film thickness t = 35–50 nm is sufficiently large to preserve the continuous morphology in most cases. The film-substrate interface has been studied with X-ray photoemission spectroscopy depth profiles and is found that there is a graded silicon-rich cobalt silicide, presumably formed during the film growth. This graded interface is of uncertain small thickness but the range of compositions clearly makes it a magnetically dead layer. On the other hand, the ripple surface rules both the magnetic coercivity and the uniaxial anisotropy as these are found to correlate with the pattern dimensions. Remarkably, the saturation fields in the hard axis of uniaxial continuous films are measured up to values as high as 0.80 kG and obey a linear dependence on the parameter ω{sup 2}/Λ/t in quantitative

  4. Perpendicular magnetic anisotropy in CoXPd100-X alloys for magnetic tunnel junctions

    Science.gov (United States)

    Clark, B. D.; Natarajarathinam, A.; Tadisina, Z. R.; Chen, P. J.; Shull, R. D.; Gupta, S.

    2017-08-01

    CoFeB/MgO-based perpendicular magnetic tunnel junctions (p-MTJ's) with high anisotropy and low damping are critical for spin-torque transfer random access memory (STT-RAM). Most schemes of making the pinned CoFeB fully perpendicular require ferrimagnets with high damping constants, a high temperature-grown L10 alloy, or an overly complex multilayered synthetic antiferromagnet (SyAF). We report a compositional study of perpendicular CoxPd alloy-pinned Co20Fe60B20/MgO based MTJ stacks, grown at moderate temperatures in a planetary deposition system. The perpendicular anisotropy of the CoxPd alloy films can be tuned based on the layer thickness and composition. The films were characterized by alternating gradient magnetometry (AGM), energy-dispersive X-rays (EDX), and X-ray diffraction (XRD). Current-in-plane tunneling (CIPT) measurements have also been performed on the compositionally varied CoxPd MTJ stacks. The CoxPd alloy becomes fully perpendicular at approximately x = 30% (atomic fraction) Co. Full-film MTJ stacks of Si/SiO2/MgO (13)/CoXPd100-x (50)/Ta (0.3)/CoFeB (1)/MgO (1.6)/CoFeB (1)/Ta (5)/Ru (10), with the numbers enclosed in parentheses being the layer thicknesses in nm, were sputtered onto thermally oxidized silicon substrates and in-situ lamp annealed at 400 °C for 5 min. CIPT measurements indicate that the highest TMR is observed for the CoPd composition with the highest perpendicular magnetic anisotropy.

  5. Magnetic stripes and holes: Complex domain patterns in perforated films with weak perpendicular anisotropy

    Directory of Open Access Journals (Sweden)

    F. Valdés-Bango

    2017-05-01

    Full Text Available Hexagonal antidot arrays have been patterned on weak perpendicular magnetic anisotropy NdCo films by e-beam lithography and lift off. Domain structure has been characterized by Magnetic Force Microscopy at remanence. On a local length scale, of the order of stripe pattern period, domain configuration is controlled by edge effects within the stripe pattern: stripe domains meet the hole boundary at either perpendicular or parallel orientation. On a longer length scale, in-plane magnetostatic effects dominate the system: clear superdomains are observed in the patterned film with average in-plane magnetization along the easy directions of the antidot array, correlated over several antidot array cells.

  6. Magnetic stripes and holes: Complex domain patterns in perforated films with weak perpendicular anisotropy

    Science.gov (United States)

    Valdés-Bango, F.; Vélez, M.; Alvarez-Prado, L. M.; Alameda, J. M.; Martín, J. I.

    2017-05-01

    Hexagonal antidot arrays have been patterned on weak perpendicular magnetic anisotropy NdCo films by e-beam lithography and lift off. Domain structure has been characterized by Magnetic Force Microscopy at remanence. On a local length scale, of the order of stripe pattern period, domain configuration is controlled by edge effects within the stripe pattern: stripe domains meet the hole boundary at either perpendicular or parallel orientation. On a longer length scale, in-plane magnetostatic effects dominate the system: clear superdomains are observed in the patterned film with average in-plane magnetization along the easy directions of the antidot array, correlated over several antidot array cells.

  7. Interplay of uniaxial and cubic anisotropy in epitaxial Fe thin films on MgO (001 substrate

    Directory of Open Access Journals (Sweden)

    Srijani Mallik

    2014-09-01

    Full Text Available Epitaxial Fe thin films were grown on annealed MgO(001 substrates at oblique incidence by DC magnetron sputtering. Due to the oblique growth configuration, uniaxial anisotropy was found to be superimposed on the expected four-fold cubic anisotropy. A detailed study of in-plane magnetic hysteresis for Fe on MgO thin films has been performed by Magneto Optic Kerr Effect (MOKE magnetometer. Both single step and double step loops have been observed depending on the angle between the applied field and easy axis i.e. along ⟨100⟩ direction. Domain images during magnetization reversal were captured by Kerr microscope. Domain images clearly evidence two successive and separate 90° domain wall (DW nucleation and motion along cubic easy cum uniaxial easy axis and cubic easy cum uniaxial hard axis, respectively. However, along cubic hard axis two 180° domain wall motion dominate the magnetization reversal process. In spite of having four-fold anisotropy it is essential to explain magnetization reversal mechanism in 0°< ϕ < 90° span as uniaxial anisotropy plays a major role in this system. Also it is shown that substrate rotation can suppress the effect of uniaxial anisotropy superimposed on four-fold anisotropy.

  8. T=0 phase diagram and nature of domains in ultrathin ferromagnetic films with perpendicular anisotropy

    International Nuclear Information System (INIS)

    Pighin, Santiago A.; Billoni, Orlando V.; Stariolo, Daniel A.; Cannas, Sergio A.

    2010-01-01

    We present the complete zero temperature phase diagram of a model for ultrathin films with perpendicular anisotropy. The whole parameter space of relevant coupling constants is studied in first order anisotropy approximation. Because the ground state is known to be formed by perpendicular stripes separated by Bloch walls, a standard variational approach is used, complemented with specially designed Monte Carlo simulations. We can distinguish four regimes according to the different nature of striped domains: a high anisotropy Ising regime with sharp domain walls, a saturated stripe regime with thicker walls inside which an in-plane component of the magnetization develops, a narrow canted-like regime, characterized by a sinusoidal variation of both the in-plane and the out of plane magnetization components, which upon further decrease of the anisotropy leads to an in-plane ferromagnetic state via a spin reorientation transition (SRT). The nature of domains and walls are described in some detail together with the variation of domain width with anisotropy, for any value of exchange and dipolar interactions. Our results, although strictly valid at T=0, can be valuable for interpreting data on the evolution of domain width at finite temperature, a still largely open problem.

  9. Perpendicular magnetic anisotropy and the magnetization process in CoFeB/Pd multilayer films

    DEFF Research Database (Denmark)

    Ngo, Duc-The; Quach, Duy-Truong; Hung, Tran Quang

    2014-01-01

    The perpendicular magnetic anisotropy (PMA) and dynamic magnetization-reversal process in [CoFeB t nm/Pd 1.0 nm]n(t = 0.4, 0.6, 0.8, 1.0 and 1.2 nm; n = 2 − 20) multilayer films have been studied by means of magnetic hysteresis and Kerr effect measurements. Strong and controllable PMA with an eff...

  10. Magnetisation switching in a ferromagnetic Heisenberg nanoparticle with uniaxial anisotropy: a Monte Carlo investigation

    International Nuclear Information System (INIS)

    Ledue, D.; Berche, P.E.; Patte, R.

    2004-01-01

    We investigate the thermal-activated magnetisation reversal in a single ferromagnetic nanoparticle with uniaxial anisotropy using Monte Carlo simulations. The aim of this work is to reproduce the reversal magnetisation by uniform rotation at very low temperature in the high-energy barrier hypothesis, that is to realize the Neel-Brown model. For this purpose we have considered a simple cubic nanoparticle where each site is occupied by a classical Heisenberg spin. The Hamiltonian is the sum of an exchange interaction term, a single-ion anisotropy term and a Zeeman interaction term. Our numerical data of the thermal variation of the switching field are compared to an approximated expression and previous experimental results on Co nanoparticles

  11. A phenomenological approach to study the effect of uniaxial anisotropy on the magnetization of ferromagnetic nanoparticles

    Science.gov (United States)

    Sánchez-Marín, N.; Cuchillo, A.; Knobel, M.; Vargas, P.

    2018-04-01

    We study the effect of the uniaxial anisotropy in a system of ideal, noninteracting ferromagnetic nanoparticles by means of a thermodynamical model. We show that the effect of the anisotropy can be easily assimilated in a temperature shift Ta∗, in analogy to what was proposed by Allia et al. (2001) in the case of interacting nanomagnets. The phenomenological anisotropic Ta∗ parameter can be negative, indicating an antiferromagnetic-like behavior, or positive, indicating a ferromagnetic-like character as seen in the inverse susceptibility behavior as a function of temperature. The study is done considering an easy axis distribution to take into account the anisotropy axis dispersion in real samples (texture). In the case of a volumetric uniform distribution of anisotropy axes, the net effect makes Ta∗ to vanish, and the magnetic susceptibility behaves like a conventional superparamagnetic system, whereas in the others a finite value is obtained for Ta∗ . When magnetic moment distribution is considered, the effect is to enhance the Ta∗ parameter, when the dispersion of the magnetic moments becomes wider.

  12. YCo5±x thin films with perpendicular anisotropy grown by molecular beam epitaxy

    Science.gov (United States)

    Sharma, S.; Hildebrandt, E.; Sharath, S. U.; Radulov, I.; Alff, L.

    2017-06-01

    The synthesis conditions of buffer-free (00l) oriented YCo5 and Y2Co17 thin films onto Al2O3 (0001) substrates have been explored by molecular beam epitaxy (MBE). The manipulation of the ratio of individual atomic beams of Yttrium, Y and Cobalt, Co, as well as growth rate variations allows establishing a thin film phase diagram. Highly textured YCo5±x thin films were stabilized with saturation magnetization of 517 emu/cm3 (0.517 MA/m), coercivity of 4 kOe (0.4 T), and anisotropy constant, K1, equal to 5.34 ×106 erg/cm3 (0.53 MJ/m3). These magnetic parameters and the perpendicular anisotropy obtained without additional underlayers make the material system interesting for application in magnetic recording devices.

  13. High Field Linear Magnetoresistance Sensors with Perpendicular Anisotropy L10-FePt Reference Layer

    Directory of Open Access Journals (Sweden)

    X. Liu

    2016-01-01

    Full Text Available High field linear magnetoresistance is an important feature for magnetic sensors applied in magnetic levitating train and high field positioning measurements. Here, we investigate linear magnetoresistance in Pt/FePt/ZnO/Fe/Pt multilayer magnetic sensor, where FePt and Fe ferromagnetic layers exhibit out-of-plane and in-plane magnetic anisotropy, respectively. Perpendicular anisotropy L10-FePt reference layer with large coercivity and high squareness ratio was obtained by in situ substrate heating. Linear magnetoresistance is observed in this sensor in a large range between +5 kOe and −5 kOe with the current parallel to the film plane. This L10-FePt based sensor is significant for the expansion of linear range and the simplification of preparation for future high field magnetic sensors.

  14. Spin torque switching of 20 nm magnetic tunnel junctions with perpendicular anisotropy

    Science.gov (United States)

    Gajek, M.; Nowak, J. J.; Sun, J. Z.; Trouilloud, P. L.; O'Sullivan, E. J.; Abraham, D. W.; Gaidis, M. C.; Hu, G.; Brown, S.; Zhu, Y.; Robertazzi, R. P.; Gallagher, W. J.; Worledge, D. C.

    2012-03-01

    Spin-transfer torque magnetic random access memory (STT-MRAM) is one of the most promising emerging non-volatile memory technologies. MRAM has so far been demonstrated with a unique combination of density, speed, and non-volatility in a single chip, however, without the capability to replace any single mainstream memory. In this paper, we demonstrate the basic physics of spin torque switching in 20 nm diameter magnetic tunnel junctions with perpendicular magnetic anisotropy materials. This deep scaling capability clearly indicates the STT MRAM device itself may be suitable for integration at much higher densities than previously proven.

  15. Enhancement of perpendicular magnetic anisotropy and anomalous hall effect in Co/Ni multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yiwei; Zhang, Jingyan, E-mail: jyzhang@ustb.edu.cn; Jiang, Shaolong; Liu, Qianqian; Li, Xujing; Yu, Guanghua, E-mail: ghyu@mater.ustb.edu.cn

    2016-12-15

    The perpendicular magnetic anisotropy (PMA) and the anomalous Hall effect (AHE) in Co/Ni multilayer were optimized by manipulating its interface structure (inducing HfO{sub 2} capping layer and Pt insertion) and post-annealing treatment. A strong PMA can be obtained in Co/Ni multilayers with HfO{sub 2} capping layer even after annealing at 400 °C. The heavy metal Hf may improve the interfacial spin-orbit coupling, which responsible for the enhanced PMA and high annealing stability. Moreover, the multilayer containing HfO{sub 2} capping layer also exhibited high saturation anomalous Hall resistivity through post-annealing, which is 0.85 μΩ cm after annealing at 375 °C, 211% larger than in the sample at deposited state which is only 0.27 μΩ cm. The enhancement of AHE is mainly attributed to the interface scattering through post-annealing treatment. - Highlights: • The perpendicular magnetic anisotropy and anomalous Hall effect of Co/Ni multilayer films were studied. • The PMA thermal stability of the Co/Ni ML can be enhanced by HfO{sub 2} capping layer and Pt insertion. • The anomalous Hall resistivity of Co/Ni ML covered by HfO{sub 2} was enhanced by post-annealing treatment.

  16. Perpendicular Magnetic Anisotropy in Heusler Alloy Films and Their Magnetoresistive Junctions

    Directory of Open Access Journals (Sweden)

    Atsufumi Hirohata

    2018-01-01

    Full Text Available For the sustainable development of spintronic devices, a half-metallic ferromagnetic film needs to be developed as a spin source with exhibiting 100% spin polarisation at its Fermi level at room temperature. One of the most promising candidates for such a film is a Heusler-alloy film, which has already been proven to achieve the half-metallicity in the bulk region of the film. The Heusler alloys have predominantly cubic crystalline structures with small magnetocrystalline anisotropy. In order to use these alloys in perpendicularly magnetised devices, which are advantageous over in-plane devices due to their scalability, lattice distortion is required by introducing atomic substitution and interfacial lattice mismatch. In this review, recent development in perpendicularly-magnetised Heusler-alloy films is overviewed and their magnetoresistive junctions are discussed. Especially, focus is given to binary Heusler alloys by replacing the second element in the ternary Heusler alloys with the third one, e.g., MnGa and MnGe, and to interfacially-induced anisotropy by attaching oxides and metals with different lattice constants to the Heusler alloys. These alloys can improve the performance of spintronic devices with higher recording capacity.

  17. Perpendicular Magnetic Anisotropy in FePt Patterned Media Employing a CrV Seed Layer

    Directory of Open Access Journals (Sweden)

    Chun Dong

    2011-01-01

    Full Text Available Abstract A thin FePt film was deposited onto a CrV seed layer at 400°C and showed a high coercivity (~3,400 Oe and high magnetization (900–1,000 emu/cm3 characteristic of L10 phase. However, the magnetic properties of patterned media fabricated from the film stack were degraded due to the Ar-ion bombardment. We employed a deposition-last process, in which FePt film deposited at room temperature underwent lift-off and post-annealing processes, to avoid the exposure of FePt to Ar plasma. A patterned medium with 100-nm nano-columns showed an out-of-plane coercivity fivefold larger than its in-plane counterpart and a remanent magnetization comparable to saturation magnetization in the out-of-plane direction, indicating a high perpendicular anisotropy. These results demonstrate the high perpendicular anisotropy in FePt patterned media using a Cr-based compound seed layer for the first time and suggest that ultra-high-density magnetic recording media can be achieved using this optimized top-down approach.

  18. Perpendicular magnetic anisotropy of amorphous ferromagnetic CoSiB/[Pt,Au] multilayer

    International Nuclear Information System (INIS)

    Jeong, S.; Yim, H. I.

    2012-01-01

    Perpendicular magnetic anisotropy is being widely studied as a possible candidate for a high density spin-transfer torque magnetic random access memory. The key issues of a high-density spin-transfer torque magnetic random access memory are decreasing the switching current and the high thermal stability. In order to solve these problems, two approaches are suggested: One is the development a new amorphous ferromagnetic material as a pinned layer for a multilayer with a low saturated magnetization (M s ) value because of the interface roughness between the two layers. The other is a search for the most suitable materials with high perpendicular magnetic anisotropy in order to have high thermal stability. In this work, we present an amorphous ferromagnetic Co 75 Si 15 B 10 material and compare the magnetic properties of a [CoSiB (0.3, 0.4, 0.5 nm)/Pt (1.4 nm)] 5 multilayer and new combinations [CoSiB (0.3, 0.4, 0.5 nm)/Au (1.5 nm)] 5 .

  19. Hysteresis, critical fields and superferromagnetism of the film with perpendicular anisotropy

    International Nuclear Information System (INIS)

    Kalita, V.M.; Kulyk, M.M.; Ryabchenko, S.M.

    2016-01-01

    This paper is focused on the analysis of hysteresis and critical phenomena of magnetization reversal of superferromagnetic (SFM) state in nanogranular (NG) Co/Al 2 O 3 film with perpendicular anisotropy. It was demonstrated that the transition from the multidomain SFM state to the homogeneous SFM state, during the magnetization process, occurs critically. The value of the field of critical transition to the homogeneous state depends on the demagnetization field, granular anisotropy and interparticle exchange anisotropy. It turned out that the temperature dependence of the coercive force of the film, despite its SFM state, accords with the Neel–Brown formula for anisotropic single-domain ferromagnetic particles, but has an anomalous angular dependence. It was concluded that domain wall motion affects these features of the coercive field. The domain wall movement may occur due to the overturn of magnetic moments of particles in the boundaries between the superdomains. At the same time, the main factors influencing the coercivity are the anisotropy of the particles, which blocks their magnetic moment reorientation, and demagnetizing factor of the film. Together they lead to the anomalous angular dependence of the coercive field. - Highlights: • The transition from the multidomain SFM to homogeneous SFM state occurs critically. • The value of the critical field depends on the direction of the magnetizing field. • Critical transition field depends on the anisotropy of the interparticle exchange. • Dependence of H c (θ H ) differs from expected one for an ensemble of the particles. • Magnetization reversal occurs by turning the particle's moments in domain borders.

  20. Perpendicular magnetic anisotropy of CoFeB\\Ta bilayers on ALD HfO2

    Directory of Open Access Journals (Sweden)

    Bart F. Vermeulen

    2017-05-01

    Full Text Available Perpendicular magnetic anisotropy (PMA is an essential condition for CoFe thin films used in magnetic random access memories. Until recently, interfacial PMA was mainly known to occur in materials stacks with MgO\\CoFe(B interfaces or using an adjacent crystalline heavy metal film. Here, PMA is reported in a CoFeB\\Ta bilayer deposited on amorphous high-κ dielectric (relative permittivity κ=20 HfO2, grown by atomic layer deposition (ALD. PMA with interfacial anisotropy energy Ki up to 0.49 mJ/m2 appears after annealing the stacks between 200°C and 350°C, as shown with vibrating sample magnetometry. Transmission electron microscopy shows that the decrease of PMA starting from 350°C coincides with the onset of interdiffusion in the materials. High-κ dielectrics are potential enablers for giant voltage control of magnetic anisotropy (VCMA. The absence of VCMA in these experiments is ascribed to a 0.6 nm thick magnetic dead layer between HfO2 and CoFeB. The results show PMA can be easily obtained on ALD high-κ dielectrics.

  1. Perpendicular magnetic anisotropy in Mn2VIn (001) films: An ab initio study

    Science.gov (United States)

    Zipporah, Muthui; Robinson, Musembi; Julius, Mwabora; Arti, Kashyap

    2018-05-01

    First principles study of the magnetic anisotropy of Mn2VIn (001) films show perpendicular magnetic anisotropy (PMA), which increases as a function of the thickness of the film. Density functional theory (DFT) as implemented in the Vienna Ab initio simulation package (VASP) is employed here to perform a comprehensive theoretical investigation of the structural, electronic and magnetic properties of the Mn2VIn(001) films of varying thickness. Our calculations were performed on fully relaxed structures, with five to seventeen mono layers (ML). The degree of spin polarization is higher in the (001) Mn2VIn thin films as compared to the bulk in contrast to what is usually the case and as in Mn2VAl, which is isoelectronic to Mn2VIn as well as inCo2VIn (001) films studied for comparison. Tetragonal distortions are found in all the systems after relaxation. The distortion in the Mn2VIn system persists even for the 17ML thin film, resulting in PMA in the Mn2VIn system. This significant finding has potential to contribute to spin transfer torque (STT) and magnetic random access memory MRAM applications, as materials with PMA derived from volume magnetocrystalline anisotropy are being proposed as ideal magnetic electrodes.

  2. On the in-plane uniaxial anisotropy formation by using Fe–Co–Zr–N films: A theoretical and experimental investigation

    Energy Technology Data Exchange (ETDEWEB)

    Seemann, K., E-mail: klaus.seemann@kit.edu; Beirle, S.; Leiste, H.

    2016-09-01

    In the present paper a simple theoretical approach for the in-plane uniaxial anisotropy evolution in thin films is introduced. In order to show, what are the conditions for a uniaxial anisotropy formation during annealing a ferromagnetic film in an external static magnetic field, a Hamiltonian, i.e., mean energy balances were established with introducing their annealing temperature dependence. At this point, a 1-dimesional chain-like arrangement of Fe and Co elements for an “isotropic” and uniaxial anisotropy state for the numerical computation was assumed. It was shown that a critical energy and annealing temperature (temperature threshold) can be attained from which a uniaxial anisotropy arises. Comparatively, calculations according to the Neél theory delivered the activation energy for inducing a uniaxial anisotropy. The experimental verification of the calculations, by using Fe{sub 40}Co{sub 37}Zr{sub 11}N{sub 12} films which were produced by reactive magnetron sputtering, yielded the activation energy of about 250 meV. Annealing temperatures above 473 K (200 °C) enabled marked uniaxial anisotropies. This correlated with the numerical quantum mechanical estimations which yielded a critical annealing temperature of approximately 449 K (176 °C). The calculated critical energy of 243 meV was in a good agreement with the verified experiments if one assumes a short range order of at least 10 ferromagnetic atoms in line (5Fe+5Co) for computation. - Highlights: • Model and theoretical description of the uniaxial anisotropy in ferromagnetic films. • Critical energy and a critical temperature for inducing the uniaxial anisotropy. • Investigation of the activation energy for inducing the uniaxial anisotropy. • Comparison with the model and according to the Neél theory.

  3. Magnetic ground and remanent states of synthetic metamagnets with perpendicular anisotropy

    International Nuclear Information System (INIS)

    Kiselev, N S; Roessler, U K; Bogdanov, A N; Hellwig, O

    2011-01-01

    In this work, we summarize our theoretical results within a phenomenological micromagnetic approach for magnetic ground state and nonequilibrium states as topological magnetic defects in multilayers with strong perpendicular anisotropy and antiferromagnetic (AF) interlayer exchange coupling (IEC), e.g. [Co/Pt(Pd)]/Ru(Ir, NiO). We give detailed analysis of our model together with the most representative results which elucidate common features of such systems. We discuss phase diagrams of the magnetic ground state, and compare solutions of our model with experimental data. A model to assess the stability of so-called tiger tail patterns is presented. It is found that these modulated topological defect cannot be stabilized by an interplay between magnetostatic and IEC energies only. It is argued that tiger tail patterns arise as nuclei of ferro-stripe structure in AF domain walls and that they are stabilized by domain wall pinning.

  4. Stochastic simulation of thermally assisted magnetization reversal in sub-100 nm dots with perpendicular anisotropy

    International Nuclear Information System (INIS)

    Purnama, Budi; Koga, Masashi; Nozaki, Yukio; Matsuyama, Kimihide

    2009-01-01

    Thermally assisted magnetization reversal of sub-100 nm dots with perpendicular anisotropy has been investigated using a micromagnetic Langevin model. The performance of the two different reversal modes of (i) a reduced barrier writing scheme and (ii) a Curie point writing scheme are compared. For the reduced barrier writing scheme, the switching field H swt decreases with an increase in writing temperature but is still larger than that of the Curie point writing scheme. For the Curie point writing scheme, the required threshold field H th , evaluated from 50 simulation results, saturates at a value, which is not simply related to the energy barrier height. The value of H th increases with a decrease in cooling time owing to the dynamic aspects of the magnetic ordering process. Dependence of H th on material parameters and dot sizes has been systematically studied

  5. Magneto-Seebeck effect in magnetic tunnel junctions with perpendicular anisotropy

    Directory of Open Access Journals (Sweden)

    Keyu Ning

    2017-01-01

    Full Text Available As one invigorated filed of spin caloritronics combining with spin, charge and heat current, the magneto-Seebeck effect has been experimentally and theoretically studied in spin tunneling thin films and nanostructures. Here we analyze the tunnel magneto-Seebeck effect in magnetic tunnel junctions with perpendicular anisotropy (p-MTJs under various measurement temperatures. The large tunnel magneto-Seebeck (TMS ratio up to −838.8% for p-MTJs at 200 K is achieved, with Seebeck coefficient S in parallel and antiparallel states of 6.7 mV/K and 62.9 mV/K, respectively. The temperature dependence of the tunnel magneto-Seebeck can be attributed to the contributing transmission function and electron states at the interface between CoFeB electrode and MgO barrier.

  6. Relaxation dynamics of magnetization transitions in synthetic antiferromagnet with perpendicular anisotropy

    Science.gov (United States)

    Talantsev, A.; Lu, Y.; Fache, T.; Lavanant, M.; Hamadeh, A.; Aristov, A.; Koplak, O.; Morgunov, R.; Mangin, S.

    2018-04-01

    Two synthetic antiferromagnet bilayer systems with strong perpendicular anisotropy CoFeB/Ta/CoFeB and Pt/Co/Ir/Co/Pt have been grown using sputtering techniques. For both systems two types of magnetization transitions have been studied. The first one concerns transitions from a state where magnetizations of the two magnetic layers are parallel (P state) to a state where magnetizations of the two layers are aligned antiparallel (AP state). The second one concerns transitions between the two possible antiparallel alignments (AP+  to AP-). For both systems and both transitions after-effect measurements can be understood in the frame of nucleation—propagation model. Time derivative analysis of magnetic relaxation curves and mapping of the first order reversal curves at different temperature allowed us to demonstrate the presence of different pinning centers, which number can be controlled by magnetic field and temperature.

  7. Magnetotransport properties of Cr1−δTe thin films with strong perpendicular magnetic anisotropy

    Directory of Open Access Journals (Sweden)

    L. Zhou

    2017-12-01

    Full Text Available P-type ferromagnetic Cr1-δTe thin films with the Curie temperature of 170K were epitaxially grown on GaAs substrate. Low-temperature magnetotransport study reveals that the film has a strong perpendicular magnetic anisotropy (PMA and an anisotropic magnetoresistance (AMR ratio up to 8.1%. Furthermore, reduced anomalous Hall effect is observed at low temperatures in Cr1-δTe, suggesting the possible crossover of the contribution to AHE from the intrinsic mechanism to extrinsic skew scattering. Distinctive from conventional transition metal ferromagnets, the AMR ratio is also greatly suppressed at low temperatures. Our work demonstrates that epitaxial Cr1-δTe films are interesting platforms for studying the physics underlying the strong PMA and large AMR.

  8. Perpendicular magnetic anisotropy and magnetization dynamics in oxidized CoFeAl films

    Science.gov (United States)

    Wu, Di; Zhang, Zhe; Li, Le; Zhang, Zongzhi; Zhao, H. B.; Wang, J.; Ma, B.; Jin, Q. Y.

    2015-07-01

    Half-metallic Co-based full-Heusler alloys with perpendicular magnetic anisotropy (PMA), such as Co2FeAl in contact with MgO, are receiving increased attention recently due to its full spin polarization for high density memory applications. However, the PMA induced by MgO interface can only be realized for very thin magnetic layers (usually below 1.3 nm), which would have strong adverse effects on the material properties of spin polarization, Gilbert damping parameter, and magnetic stability. In order to solve this issue, we fabricated oxidized Co50Fe25Al25 (CFAO) films with proper thicknesses without employing the MgO layer. The samples show controllable PMA by tuning the oxygen pressure (PO2) and CFAO thickness (tCFAO), large perpendicular anisotropy field of ~8.0 kOe can be achieved at PO2 = 12% for the sample of tCFAO = 2.1 nm or at PO2 = 7% for tCFAO = 2.8 nm. The loss of PMA at thick tCFAO or high PO2 results mainly from the formation of large amount of CoFe oxides, which are superparamagnetic at room temperature but become hard magnetic at low temperatures. The magnetic CFAO films, with strong PMA in a relatively wide thickness range and small intrinsic damping parameter below 0.028, would find great applications in developing advanced spintronic devices.

  9. Magnetization reversal mechanism of Nd-Fe-B films with perpendicular magnetic anisotropy

    International Nuclear Information System (INIS)

    Liu Xiaoxi; Ishida, Go; Morisako, Akimitsu

    2011-01-01

    The microstructure and magnetic properties of Nd-Fe-B films with thicknesses from 100 nm to 3 nm have been investigated. All the films show excellent perpendicular magnetic anisotropy with a squareness ratio of 1 in the perpendicular direction and almost zero coercivity in the in-plane direction. Of particular interest is that the initial magnetization curves sensitively depended on the film thickness. Films thicker than 15 nm show steep initial magnetization curve. Although the films have coercivities larger than 21 kOe, the films can be fully magnetized from the thermally demagnetized state with a field as small as 5 kOe. With the decrease of film thickness to 5 nm, the initial magnetization curve becomes flat. The evolution of initial magnetization curves with film thickness can be understood by the microstructure of the films. Films with thickness of 15 nm show close-packed grains without any intergranular phases. Such microstructures lead to steep initial magnetization curves. On the other hand, when the film thickness decreased to 3 nm, the film thickness became nonuniform. Such microstructure leads to flat initial magnetization curves.

  10. Micromagnetic study of skyrmion stability in confined magnetic structures with perpendicular anisotropy

    Science.gov (United States)

    Novak, R. L.; Garcia, F.; Novais, E. R. P.; Sinnecker, J. P.; Guimarães, A. P.

    2018-04-01

    Skyrmions are emerging topological spin structures that are potentially revolutionary for future data storage and spintronics applications. The existence and stability of skyrmions in magnetic materials is usually associated to the presence of the Dzyaloshinskii-Moriya interaction (DMI) in bulk magnets or in magnetic thin films lacking inversion symmetry. While some methods have already been proposed to generate isolated skyrmions in thin films with DMI, a thorough study of the conditions under which the skyrmions will remain stable in order to be manipulated in an integrated spintronic device are still an open problem. The stability of such structures is believed to be a result of ideal combinations of perpendicular magnetic anisotropy (PMA), DMI and the interplay between geometry and magnetostatics. In the present work we show some micromagnetic results supporting previous experimental observations of magnetic skyrmions in spin-valve stacks with a wide range of DMI values. Using micromagnetic simulations of cobalt-based disks, we obtain the magnetic ground state configuration for several values of PMA, DMI and geometric parameters. Skyrmion numbers, corresponding to the topological charge, are calculated in all cases and confirm the occurrence of isolated, stable, axially symmetric skyrmions for several combinations of DMI and anisotropy constant. The stability of the skyrmions in disks is then investigated under magnetic field and spin-polarized current, in finite temperature, highlighting the limits of applicability of these spin textures in spintronic devices.

  11. Origin of interfacial perpendicular magnetic anisotropy in MgO/CoFe/metallic capping layer structures.

    Science.gov (United States)

    Peng, Shouzhong; Wang, Mengxing; Yang, Hongxin; Zeng, Lang; Nan, Jiang; Zhou, Jiaqi; Zhang, Youguang; Hallal, Ali; Chshiev, Mairbek; Wang, Kang L; Zhang, Qianfan; Zhao, Weisheng

    2015-12-11

    Spin-transfer-torque magnetic random access memory (STT-MRAM) attracts extensive attentions due to its non-volatility, high density and low power consumption. The core device in STT-MRAM is CoFeB/MgO-based magnetic tunnel junction (MTJ), which possesses a high tunnel magnetoresistance ratio as well as a large value of perpendicular magnetic anisotropy (PMA). It has been experimentally proven that a capping layer coating on CoFeB layer is essential to obtain a strong PMA. However, the physical mechanism of such effect remains unclear. In this paper, we investigate the origin of the PMA in MgO/CoFe/metallic capping layer structures by using a first-principles computation scheme. The trend of PMA variation with different capping materials agrees well with experimental results. We find that interfacial PMA in the three-layer structures comes from both the MgO/CoFe and CoFe/capping layer interfaces, which can be analyzed separately. Furthermore, the PMAs in the CoFe/capping layer interfaces are analyzed through resolving the magnetic anisotropy energy by layer and orbital. The variation of PMA with different capping materials is attributed to the different hybridizations of both d and p orbitals via spin-orbit coupling. This work can significantly benefit the research and development of nanoscale STT-MRAM.

  12. High quality TmIG films with perpendicular magnetic anisotropy grown by sputtering

    Science.gov (United States)

    Wu, C. N.; Tseng, C. C.; Yeh, S. L.; Lin, K. Y.; Cheng, C. K.; Fanchiang, Y. T.; Hong, M.; Kwo, J.

    Ferrimagnetic thulium iron garnet (TmIG) films grown on gadolinium gallium garnet substrates recently showed stress-induced perpendicular magnetic anisotropy (PMA), attractive for realization of quantum anomalous Hall effect (QAHE) of topological insulator (TI) films via the proximity effect. Moreover, current induced magnetization switching of Pt/TmIG has been demonstrated for the development of room temperature (RT) spintronic devices. In this work, high quality TmIG films (about 25nm) were grown by sputtering at RT followed by post-annealing. We showed that the film composition is tunable by varying the growth parameters. The XRD results showed excellent crystallinity of stoichiometric TmIG films with an out-of-plane lattice constant of 1.2322nm, a narrow film rocking curve of 0.017 degree, and a film roughness of 0.2 nm. The stoichiometric films exhibited PMA and the saturation magnetization at RT was 109 emu/cm3 (RT bulk value 110 emu/cm3) with a coercive field of 2.7 Oe. In contrast, TmIG films of Fe deficiency showed in-plane magnetic anisotropy. The high quality sputtered TmIG films will be applied to heterostructures with TIs or metals with strong spin-orbit coupling for novel spintronics.

  13. Perpendicular magnetic anisotropy in granular multilayers of CoPd alloyed nanoparticles

    Science.gov (United States)

    Vivas, L. G.; Rubín, J.; Figueroa, A. I.; Bartolomé, F.; García, L. M.; Deranlot, C.; Petroff, F.; Ruiz, L.; González-Calbet, J. M.; Pascarelli, S.; Brookes, N. B.; Wilhelm, F.; Chorro, M.; Rogalev, A.; Bartolomé, J.

    2016-05-01

    Co-Pd multilayers obtained by Pd capping of pre-deposited Co nanoparticles on amorphous alumina are systematically studied by means of high-resolution transmission electron microscopy, x-ray diffraction, extended x-ray absorption fine structure, SQUID-based magnetometry, and x-ray magnetic circular dichroism. The films are formed by CoPd alloyed nanoparticles self-organized across the layers, with the interspace between the nanoparticles filled by the non-alloyed Pd metal. The nanoparticles show atomic arrangements compatible with short-range chemical order of L 10 strucure type. The collective magnetic behavior is that of ferromagnetically coupled particles with perpendicular magnetic anisotropy, irrespective of the amount of deposited Pd. For increasing temperature three magnetic phases are identified: hard ferromagnetic with strong coercive field, soft-ferromagnetic as in an amorphous asperomagnet, and superparamagnetic. Increasing the amount of Pd in the system leads to both magnetic hardness increment and higher transition temperatures. Magnetic total moments of 1.77(4) μB and 0.45(4) μB are found at Co and Pd sites, respectively, where the orbital moment of Co, 0.40(2) μB, is high, while that of Pd is negligible. The effective magnetic anisotropy is the largest in the capping metal series (Pd, Pt, W, Cu, Ag, Au), which is attributed to the interparticle interaction between de nanoparticles, in addition to the intraparticle anisotropy arising from hybridization between the 3 d -4 d bands associated to the Co and Pd chemical arrangement in a L 10 structure type.

  14. Ferromagnetic resonance linewidth and damping in perpendicular-anisotropy magnetic multilayers thin films

    Science.gov (United States)

    Beaujour, Jean-Marc

    2010-03-01

    Transition metal ferromagnetic films with perpendicular magnetic anisotropy (PMA) have ferromagnetic resonance (FMR) linewidths that are one order of magnitude larger than soft magnetic materials, such as pure iron (Fe) and permalloy (NiFe) thin films. We have conducted systematic studies of a variety of thin film materials with perpendicular magnetic anisotropy to investigate the origin of the enhanced FMR linewidths, including Ni/Co and CoFeB/Co/Ni multilayers. In Ni/Co multilayers the PMA was systematically reduced by irradiation with Helium ions, leading to a transition from out-of-plane to in-plane easy axis with increasing He ion fluence [1,2]. The FMR linewidth depends linearly on frequency for perpendicular applied fields and increases significantly when the magnetization is rotated into the film plane with an applied in-plane magnetic field. Irradiation of the film with Helium ions decreases the PMA and the distribution of PMA parameters, leading to a large reduction in the FMR linewidth for in-plane magnetization. These results suggest that fluctuations in the PMA lead to a large two magnon scattering contribution to the linewidth for in-plane magnetization and establish that the Gilbert damping is enhanced in such materials (α˜0.04, compared to α˜0.002 for pure Fe) [2]. We compare these results to those on CoFeB/Co/Ni and published results on other thin film materials with PMA [e.g., Ref. 3]. [1] D. Stanescu et al., J. Appl. Phys. 103, 07B529 (2008). [2] J-M. L. Beaujour, D. Ravelosona, I. Tudosa, E. Fullerton, and A. D. Kent, Phys. Rev. B RC 80, 180415 (2009). [3] N. Mo, J. Hohlfeld, M. ulIslam, C. S. Brown, E. Girt, P. Krivosik, W. Tong, A. Rebel, and C. E. Patton, Appl. Phys. Lett. 92, 022506 (2008). *Research done in collaboration with: A. D. Kent, New York University, D. Ravelosona, Institut d'Electronique Fondamentale, UMR CNRS 8622, Universit'e Paris Sud, E. E. Fullerton, Center for Magnetic Recording Research, UCSD, and supported by NSF

  15. Lack of dependence between intrinsic magnetic damping and perpendicular magnetic anisotropy in Cu(t{sub Cu})/[Ni/Co]{sub N} multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Minghong [Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education), Department of Optical Science and Engineering, Fudan University, Shanghai 200433 (China); Li, Wei [State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062 (China); Ren, Yang [School of Physics and Astronomy, Yunnan University, Kunming 650000 (China); Zhang, Zongzhi, E-mail: zzzhang@fudan.edu.cn [Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education), Department of Optical Science and Engineering, Fudan University, Shanghai 200433 (China); Jin, Q.Y. [Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education), Department of Optical Science and Engineering, Fudan University, Shanghai 200433 (China)

    2017-04-15

    The correlation between magnetic damping and perpendicular magnetic anisotropy has been investigated in Cu(t{sub Cu})/[Ni/Co]{sub N} multilayers by time-resolved magneto-optical Kerr effect. The uniaxial magnetic anisotropy constant K{sub u} is varied in the range of 3.0–3.6 Merg/cm{sup 3} by tuning either multilayer repetition number N or Cu thickness t{sub Cu}. It is found that the PMA strength K{sub u} increases with the increase of N, while the damping constant α{sub 0} keeps nearly a constant of 0.025, implying the intrinsic damping is independent of the K{sub u} tuned by N. In contrast, as t{sub Cu} increases from 2.5 to 20 nm, the α{sub 0} value rises continuously up to 0.040, in spite of the rather weak enhancement in K{sub u} and its non-monotonic variation behavior. We consider the constant α{sub 0} with N is due to the unchanged spin-orbit coupling strength at each Co/Ni interface, while the obvious enhancement in α{sub 0} with t{sub Cu} results mainly from the increased degree of spin disordering at the rougher Cu/Ni interface. - Highlights: • The perpendicular magnetic anisotropy K{sub u} is tuned in Cu(t{sub Cu})/[Ni/Co]{sub N} system. • The intrinsic magnetic damping is found to be independent K{sub u}. • Extrinsic damping increases with t{sub Cu} due to large interfacial spin disordering.

  16. Exchange bias energy in Co/Pt/IrMn multilayers with perpendicular and in-plane anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Czapkiewicz, M. [Department of Electronics, AGH University of Science and Technology, 30-059 Cracow (Poland)]. E-mail: czapkiew@agh.edu.pl; Stobiecki, T. [Department of Electronics, AGH University of Science and Technology, 30-059 Cracow (Poland); Rak, R. [Department of Electronics, AGH University of Science and Technology, 30-059 Cracow (Poland); Zoladz, M. [Department of Electronics, AGH University of Science and Technology, 30-059 Cracow (Poland); Dijken, S. van [CRANN and School of Physics, Trinity College, Dublin 2 (Ireland)

    2007-09-15

    The magnetization reversal process in perpendicularly biased [Pt/Co]{sub 3}/d{sub Pt} Pt/IrMn and in-plane biased Co/d{sub Pt} Pt/IrMn multilayers with 0nm=anisotropy, the exchange bias field decreases monotonically with Pt insertion layer thickness, while its coercivity remains constant. The samples with perpendicular magnetic anisotropy, on the other hand, exhibit maximum exchange bias and minimum coercivity for d{sub Pt}=0.1nm. In both cases, the existence of large exchange bias fields correlates with a high domain density during magnetization reversal. The interface exchange coupling energy is larger for the in-plane biased films than for the perpendicularly biased multilayers.

  17. Spin-Orbit Torque-Assisted Switching in Magnetic Insulator Thin Films with Perpendicular Magnetic Anisotropy

    Science.gov (United States)

    Wu, Mingzhong

    As an in-plane charge current flows in a heavy metal film with spin-orbit coupling, it produces a torque that can induce magnetization switching in a neighboring ferromagnetic metal film. Such spin-orbit torque (SOT)-induced switching has been studied extensively in recent years and has shown higher efficiency than switching using conventional spin-transfer torque. This presentation reports the SOT-assisted switching in heavy metal/magnetic insulator systems.1 The experiments made use of Pt/BaFe12O19 bi-layered structures. Thanks to its strong spin-orbit coupling, Pt has been widely used to produce pure spin currents in previous studies. BaFe12O19 is an M-type barium hexagonal ferrite and is often referred as BaM. It is one of the few magnetic insulators with strong magneto-crystalline anisotropy and shows an effective uniaxial anisotropy field of about 17 kOe. It's found that the switching response in the BaM film strongly depends on the charge current applied to the Pt film. When a constant magnetic field is applied in the film plane, the charge current in the Pt film can switch the normal component of the magnetization (M⊥) in the BaM film between the up and down states. The current also dictates the up and down states of the remnant magnetization when the in-plane field is reduced to zero. When M⊥ is measured by sweeping an in-plane field, the response manifests itself as a hysteresis loop, which evolves in a completely opposite manner if the sign of the charge current is flipped. When the coercivity is measured by sweeping an out-of-plane field, its value can be reduced or increased by as much as about 500 Oe if an appropriate charge current is applied. 1. P. Li, T. Liu, H. Chang, A. Kalitsov, W. Zhang, G. Csaba, W. Li, D. Richardson, A. Demann, G. Rimal, H. Dey, J. S. Jiang, W. Porod, S. Field, J. Tang, M. C. Marconi, A. Hoffmann, O. Mryasov, and M. Wu, Nature Commun. 7:12688 doi: 10.1038/ncomms12688 (2016).

  18. The stochastic nature of the domain wall motion along high perpendicular anisotropy strips with surface roughness

    International Nuclear Information System (INIS)

    Martinez, Eduardo

    2012-01-01

    The domain wall dynamics along thin ferromagnetic strips with high perpendicular magnetocrystalline anisotropy driven by either magnetic fields or spin-polarized currents is theoretically analyzed by means of full micromagnetic simulations and a one-dimensional model, including both surface roughness and thermal effects. At finite temperature, the results show a field dependence of the domain wall velocity in good qualitative agreement with available experimental measurements, indicating a low field, low velocity creep regime, and a high field, linear regime separated by a smeared depinning region. Similar behaviors were also observed under applied currents. In the low current creep regime the velocity-current characteristic does not depend significantly on the non-adiabaticity. At high currents, where the domain wall velocity becomes insensitive to surface pinning, the domain wall shows a precessional behavior even when the non-adiabatic parameter is equal to the Gilbert damping. These analyses confirm the relevance of both thermal fluctuations and surface roughness for the domain wall dynamics, and that complete micromagnetic modeling and one-dimensional studies taking into account these effects are required to interpret the experimental measurements in order to get a better understanding of the origin, the role and the magnitude of the non-adiabaticity. (paper)

  19. Spin-orbit torque induced switching in a magnetic insulator thin film with perpendicular magnetic anisotropy

    Science.gov (United States)

    Li, J. X.; Yu, G. Q.; Tang, C.; Wang, K. L.; Shi, J.

    Spin-orbit torque (SOT) has been demonstrated to be efficient to manipulate the magnetization in heavy-metal/ferromagnetic metal (HM/FMM) heterostructures. In HM/magnetic insulator (MI) heterostructures, charge currents do not flow in MI, but pure spin currents generated by the spin Hall effect in HM can enter the MI layer to cause magnetization dynamics. Here we report SOT-induced magnetization switching in Tm3Fe5O12/Pt heterostructures, where Tm3Fe5O12 (TmIG) is a MI grown by pulsed laser deposition with perpendicular magnetic anisotropy. The anomalous Hall signal in Pt is used as a probe to detect the magnetization switching. Effective magnetic fields due to the damping-like and field-like torques are extracted using a harmonic Hall detection method. The experiments are carried out in heterostructures with different TmIG film thicknesses. Both the switching and harmonic measurements indicate a more efficient SOT generation in HM/MI than in HM/FMM heterostructures. Our comprehensive experimental study and detailed analysis will be presented. This work was supported as part of the SHINES, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Basic Energy Sciences under Award No. SC0012670.

  20. Failure Analysis in Magnetic Tunnel Junction Nanopillar with Interfacial Perpendicular Magnetic Anisotropy

    Directory of Open Access Journals (Sweden)

    Weisheng Zhao

    2016-01-01

    Full Text Available Magnetic tunnel junction nanopillar with interfacial perpendicular magnetic anisotropy (PMA-MTJ becomes a promising candidate to build up spin transfer torque magnetic random access memory (STT-MRAM for the next generation of non-volatile memory as it features low spin transfer switching current, fast speed, high scalability, and easy integration into conventional complementary metal oxide semiconductor (CMOS circuits. However, this device suffers from a number of failure issues, such as large process variation and tunneling barrier breakdown. The large process variation is an intrinsic issue for PMA-MTJ as it is based on the interfacial effects between ultra-thin films with few layers of atoms; the tunneling barrier breakdown is due to the requirement of an ultra-thin tunneling barrier (e.g., <1 nm to reduce the resistance area for the spin transfer torque switching in the nanopillar. These failure issues limit the research and development of STT-MRAM to widely achieve commercial products. In this paper, we give a full analysis of failure mechanisms for PMA-MTJ and present some eventual solutions from device fabrication to system level integration to optimize the failure issues.

  1. Magnetic droplets in nano-contact spin-torque oscillators with perpendicular magnetic anisotropy

    Science.gov (United States)

    Åkerman, Johan

    2013-03-01

    The theoretical prediction, by Ivanov and Kosevich, of ``magnon drop'' solitons in thin films with perpendicular magnetic anisotropy (PMA) and zero damping, dates back to the 1970s. More recently, Hoefer, Silva and Keller, demonstrated analytically and numerically that related ``magnetic droplet'' solitons should be possible to excite in nano-contact spin-torque oscillators (NC-STOs) based on PMA materials, where spin transfer torque locally realizes the zero-damping condition required in. In my talk, I will present the first experimental demonstration of such magnetic droplets, realized using 50-100 nm diameter nano-contacts (NCs) fabricated on top of orthogonal GMR stacks of Co8/Cu/Co0.3[Ni0.8/Co0.4]x4 (thicknesses in nm). The nucleation of a magnetic droplet manifests itself as a dramatic 10 GHz drop in microwave signal frequency at a drive-current dependent critical perpendicular field of the order of 0.5 - 1 T. The drop in frequency is accompanied by a simultaneous sharp resistance increase of the device and a sign change of its magnetoresistance, directly indicating the existence of a reversed magnetization in a region of the [Co/Ni] free layer underneath the NC. As predicted by numerical simulations the droplet exhibits rich magnetodynamic properties, experimentally observed as auto-modulation at approximately 1 GHz and sometimes sidebands at 1/2 and 3/2 of the fundamental droplet frequency. The 1 GHz modulation can be shown numerically to be related to the drift instability of the droplet, albeit with enough restoring force to make the droplet perform a periodic motion instead of leaving the NC region. The sidebands at 1/2 and 3/2 the droplet frequency are related to eigenmodes of the droplet perimeter. Magnetic droplet nucleation is found to be robust and reproducible over a wide number of NC-STOs with different NC sizes, making this new nanomagnetic object as fundamental and potentially useful to nanomagnetism as e.g. domain walls and vortices. Support

  2. Evidence for nanoscale two-dimensional Co clusters in CoPt{sub 3} films with perpendicular magnetic anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Cross, J O [Department of Physics, University of Washington, Seattle, WA 98195 (United States); Newville, M [Consortium for Advanced Radiation Sources, University of Chicago, Chicago, IL 60637 (United States); Maranville, B B; Hellman, F [Department of Physics, University of California at San Diego, La Jolla, CA 92093 (United States); Bordel, C [Department of Physics, University of California at Berkeley, CA 94720 (United States); Harris, V G, E-mail: cbordel@berkeley.ed [Department of Electrical and Computer Engineering, Northeastern University, Boston, MA 02115 (United States)

    2010-04-14

    The length scale of the local chemical anisotropy responsible for the growth-temperature-induced perpendicular magnetic anisotropy of face-centered cubic CoPt{sub 3} alloy films was investigated using polarized extended x-ray absorption fine structure (EXAFS). These x-ray measurements were performed on a series of four (111) CoPt{sub 3} films epitaxially grown on (0001) sapphire substrates. The EXAFS data show a preference for Co-Co pairs parallel to the film plane when the film exhibits magnetic anisotropy, and random chemical order otherwise. Furthermore, atomic pair correlation anisotropy was evidenced only in the EXAFS signal from the next neighbors to the absorbing Co atoms and from multiple scattering paths focused through the next neighbors. This suggests that the Co clusters are no more than a few atoms in extent in the plane and one monolayer in extent out of the plane. Our EXAFS results confirm the correlation between perpendicular magnetic anisotropy and two-dimensional Co segregation in CoPt{sub 3} alloy films, and establish a length scale on the order of 10 A for the Co clusters.

  3. Asymmetric driven dynamics of Dzyaloshinskii domain walls in ultrathin ferromagnetic strips with perpendicular magnetic anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Sánchez-Tejerina, L. [Dpto. Electricidad y Electrónica, Facultad de Ciencias, Universidad de Valladolid, 47011 Valladolid (Spain); Alejos, Ó., E-mail: oscaral@ee.uva.es [Dpto. Electricidad y Electrónica, Facultad de Ciencias, Universidad de Valladolid, 47011 Valladolid (Spain); Martínez, E. [Dpto. Física Aplicada, Facultad de Ciencias, Universidad de Salamanca, 37011 Salamanca (Spain); Muñoz, J.M. [Dpto. Electricidad y Electrónica, Facultad de Ciencias, Universidad de Valladolid, 47011 Valladolid (Spain)

    2016-07-01

    The dynamics of domain walls in ultrathin ferromagnetic strips with perpendicular magnetic anisotropy is studied from both numerical and analytical micromagnetics. The influence of a moderate interfacial Dzyaloshinskii–Moriya interaction associated to a bi-layer strip arrangement has been considered, giving rise to the formation of Dzyaloshinskii domain walls. Such walls possess under equilibrium conditions an inner magnetization structure defined by a certain orientation angle that make them to be considered as intermediate configurations between Bloch and Néel walls. Two different dynamics are considered, a field-driven and a current-driven dynamics, in particular, the one promoted by the spin torque due to the spin-Hall effect. Results show an inherent asymmetry associated with the rotation of the domain wall magnetization orientation before reaching the stationary regime, characterized by a constant terminal speed. For a certain initial DW magnetization orientation at rest, the rotation determines whether the reorientation of the DW magnetization prior to reach stationary motion is smooth or abrupt. This asymmetry affects the DW motion, which can even reverse for a short period of time. Additionally, it is found that the terminal speed in the case of the current-driven dynamics may depend on either the initial DW magnetization orientation at rest or the sign of the longitudinally injected current. - Highlights: • The asymmetric response of domain walls in bilayer strips with PMA is studied. • Out-of-plane fields and SHE longitudinal currents are applied. • The response is associated to the rotation of the domain wall inner magnetization. • Clockwise and counter-clockwise magnetization rotations are not equivalent. • The asymmetry results in different travelled distances and/or terminal speeds.

  4. Asymmetric driven dynamics of Dzyaloshinskii domain walls in ultrathin ferromagnetic strips with perpendicular magnetic anisotropy

    International Nuclear Information System (INIS)

    Sánchez-Tejerina, L.; Alejos, Ó.; Martínez, E.; Muñoz, J.M.

    2016-01-01

    The dynamics of domain walls in ultrathin ferromagnetic strips with perpendicular magnetic anisotropy is studied from both numerical and analytical micromagnetics. The influence of a moderate interfacial Dzyaloshinskii–Moriya interaction associated to a bi-layer strip arrangement has been considered, giving rise to the formation of Dzyaloshinskii domain walls. Such walls possess under equilibrium conditions an inner magnetization structure defined by a certain orientation angle that make them to be considered as intermediate configurations between Bloch and Néel walls. Two different dynamics are considered, a field-driven and a current-driven dynamics, in particular, the one promoted by the spin torque due to the spin-Hall effect. Results show an inherent asymmetry associated with the rotation of the domain wall magnetization orientation before reaching the stationary regime, characterized by a constant terminal speed. For a certain initial DW magnetization orientation at rest, the rotation determines whether the reorientation of the DW magnetization prior to reach stationary motion is smooth or abrupt. This asymmetry affects the DW motion, which can even reverse for a short period of time. Additionally, it is found that the terminal speed in the case of the current-driven dynamics may depend on either the initial DW magnetization orientation at rest or the sign of the longitudinally injected current. - Highlights: • The asymmetric response of domain walls in bilayer strips with PMA is studied. • Out-of-plane fields and SHE longitudinal currents are applied. • The response is associated to the rotation of the domain wall inner magnetization. • Clockwise and counter-clockwise magnetization rotations are not equivalent. • The asymmetry results in different travelled distances and/or terminal speeds.

  5. Perpendicular magnetic anisotropy in Co{sub X}Pd{sub 100−X} alloys for magnetic tunnel junctions

    Energy Technology Data Exchange (ETDEWEB)

    Clark, B.D.; Natarajarathinam, A.; Tadisina, Z.R. [Center for Materials for Information Technology, University of Alabama, Tuscaloosa, AL 35487 (United States); Chen, P.J.; Shull, R.D. [National Institute of Standards and Technology, Gaithersburg, MD 20899 (United States); Gupta, S., E-mail: Sgupta@eng.ua.edu [Center for Materials for Information Technology, University of Alabama, Tuscaloosa, AL 35487 (United States)

    2017-08-15

    Highlights: • CoPd alloy perpendicular anisotropy dependent on composition and thickness. • CIPT results show that TMR tracks with PMA of CoPd. • Potential replacement for Co/Pd multilayers. - Abstract: CoFeB/MgO-based perpendicular magnetic tunnel junctions (p-MTJ’s) with high anisotropy and low damping are critical for spin-torque transfer random access memory (STT-RAM). Most schemes of making the pinned CoFeB fully perpendicular require ferrimagnets with high damping constants, a high temperature-grown L1{sub 0} alloy, or an overly complex multilayered synthetic antiferromagnet (SyAF). We report a compositional study of perpendicular Co{sub x}Pd alloy-pinned Co{sub 20}Fe{sub 60}B{sub 20}/MgO based MTJ stacks, grown at moderate temperatures in a planetary deposition system. The perpendicular anisotropy of the Co{sub x}Pd alloy films can be tuned based on the layer thickness and composition. The films were characterized by alternating gradient magnetometry (AGM), energy-dispersive X-rays (EDX), and X-ray diffraction (XRD). Current-in-plane tunneling (CIPT) measurements have also been performed on the compositionally varied Co{sub x}Pd MTJ stacks. The Co{sub x}Pd alloy becomes fully perpendicular at approximately x = 30% (atomic fraction) Co. Full-film MTJ stacks of Si/SiO{sub 2}/MgO (13)/Co{sub X}Pd{sub 100−x} (50)/Ta (0.3)/CoFeB (1)/MgO (1.6)/CoFeB (1)/Ta (5)/Ru (10), with the numbers enclosed in parentheses being the layer thicknesses in nm, were sputtered onto thermally oxidized silicon substrates and in-situ lamp annealed at 400 °C for 5 min. CIPT measurements indicate that the highest TMR is observed for the CoPd composition with the highest perpendicular magnetic anisotropy.

  6. Anisotropy and relaxation processes of uniaxially oriented CoFe2O4 nanoparticles dispersed in PDMS

    International Nuclear Information System (INIS)

    Antonel, P.S.; Negri, R.M.; Leyva, A.G.; Jorge, G.A.

    2012-01-01

    When a uniaxial magnetic field is applied to a non-magnetic dispersive medium filled with magnetic nanoparticles, they auto-assemble into thin needles parallel to the field direction, due to the strong dipolar interaction among them. We have prepared in this way magnetically oriented nanocomposites of nanometer-size CoFe 2 O 4 particles in a polydimethylsiloxane polymer matrix, with 10% w/w of magnetic particles. We present the characteristic magnetic relaxation curves measured after the application of a magnetic field forming an angle α with respect to the needle direction. We show that the magnetic viscosity (calculated from the logarithmic relaxation curves) as a function of α presents a minimum at α=0, indicating slower relaxation processes associated with this configuration of fields. The results seems to point out that the local magnetic anisotropy of the nanoparticles is oriented along the needles, resulting in the macroscopic magnetic anisotropy observed in our measurements.

  7. Anisotropy and relaxation processes of uniaxially oriented CoFe{sub 2}O{sub 4} nanoparticles dispersed in PDMS

    Energy Technology Data Exchange (ETDEWEB)

    Antonel, P.S.; Negri, R.M. [Instituto de Quimica Fisica de Materiales, Ambiente y Energia (INQUIMAE), Departamento de Quimica Inorganica, Analitica y Quimica Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellon II, Av. Cantilo s/n (1428), Buenos Aires (Argentina); Leyva, A.G. [Grupo de Materia Condensada, Gerencia de Investigacion y Aplicaciones, Centro Atomico Constituyentes, Comision Nacional de Energia Atomica, Avda. Gral. Paz 1499 (1650) San Martin, Pcia. de Buenos Aires, Argentina - Escuela de Ciencia y Tecnologia, UNSAM (Argentina); Jorge, G.A., E-mail: gjorge@df.uba.ar [Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellon I, Av. Cantilo s/n (1428), Buenos Aires (Argentina)

    2012-08-15

    When a uniaxial magnetic field is applied to a non-magnetic dispersive medium filled with magnetic nanoparticles, they auto-assemble into thin needles parallel to the field direction, due to the strong dipolar interaction among them. We have prepared in this way magnetically oriented nanocomposites of nanometer-size CoFe{sub 2}O{sub 4} particles in a polydimethylsiloxane polymer matrix, with 10% w/w of magnetic particles. We present the characteristic magnetic relaxation curves measured after the application of a magnetic field forming an angle {alpha} with respect to the needle direction. We show that the magnetic viscosity (calculated from the logarithmic relaxation curves) as a function of {alpha} presents a minimum at {alpha}=0, indicating slower relaxation processes associated with this configuration of fields. The results seems to point out that the local magnetic anisotropy of the nanoparticles is oriented along the needles, resulting in the macroscopic magnetic anisotropy observed in our measurements.

  8. Tuning the effective parameters in (Ta/Cu/[Ni/Co]x/Ta) multilayers with perpendicular magnetic anisotropy

    Science.gov (United States)

    Ayareh, Zohreh; Moradi, Mehrdad; Mahmoodi, Saman

    2018-06-01

    In this paper, we report perpendicular magnetic anisotropy (PMA) in a (Ta/Cu/[Ni/Co]x/Ta) multilayers structure. These typical structures usually include a multilayer of ferromagnetic and transition metal thin films. Usually, magnetic anisotropy is characterized by magnetization loops determined by magnetometer or magneto-optical Kerr effect (MOKE). The interface between ferromagnetic and metallic layers plays an important role in magnetic anisotropy evolution from out-of-plane to in-plane in (Ta/Cu/[Ni/Co]/Ta) structure. Obtained results from MOKE and magnetometry of these samples show that they have different easy axes due to change in thickness of Cu as spacer layer and difference in number of repetition of [Ni/Co] stacks.

  9. Electric-regulated enhanced in-plane uniaxial anisotropy in FeGa/PMN-PT composite using oblique pulsed laser deposition

    Science.gov (United States)

    Zhang, Yi; Huang, Chaojuan; Turghun, Mutellip; Duan, Zhihua; Wang, Feifei; Shi, Wangzhou

    2018-04-01

    The FeGa film with in-plane uniaxial magnetic anisotropy was fabricated onto different oriented single-crystal lead magnesium niobate-lead titanate using oblique pulsed laser deposition. An enhanced in-plane uniaxial magnetic anisotropy field of FeGa film can be adjusted from 18 Oe to 275 Oe by tuning the oblique angle and polarizing voltage. The competitive relationship of shape anisotropy and strain anisotropy has been discussed, which was induced by oblique angle and polarizing voltage, respectively. The (100)-oriented and (110)-oriented PMN-PT show completely different characters on voltage-dependent magnetic properties, which could be attributed to various anisotropy directions depended on different strain directions.

  10. Perpendicular magnetic anisotropy influence on voltage-driven spin-diode effect in magnetic tunnel junctions: A micromagnetic study

    Energy Technology Data Exchange (ETDEWEB)

    Frankowski, Marek, E-mail: mfrankow@agh.edu.pl [AGH University of Science and Technology, al. Mickiewicza 30, Department of Electronics, 30-059 Kraków (Poland); Chȩciński, Jakub [AGH University of Science and Technology, al. Mickiewicza 30, Department of Electronics, 30-059 Kraków (Poland); AGH University of Science and Technology, al. Mickiewicza 30, Faculty of Physics and Applied Computer Science, 30-059 Kraków (Poland); Skowroński, Witold; Stobiecki, Tomasz [AGH University of Science and Technology, al. Mickiewicza 30, Department of Electronics, 30-059 Kraków (Poland)

    2017-05-01

    We study the influence of the perpendicular magnetic anisotropy on the voltage-induced ferromagnetic resonance in magnetic tunnel junctions (MTJs). An MTJ response to the applied radio-frequency voltage excitation is investigated using micromagnetic calculations with the free layer oriented both in-plane and out-of-plane. Our model allows for a quantitative description of the magnetic system parameters such as resonance frequency, sensitivity or quality factor and for a distinction between material-dependent internal damping and disorder-dependent effective damping. We find that the sensitivity abruptly increases up to three orders of magnitude near the anisotropy transition regime, while the quality factor declines due to effective damping increase. We attribute the origin of this behaviour to the changes of the exchange energy in the system, which is calculated using micromagnetic approach. - Highlights: • Micromagnetic approach is used for modelling of voltage-induced spin-diode effect. • Voltage-induced switching simulations are performed. • Spin-diode line is analyzed as a function of perpendicular anisotropy energy. • Effective damping, quality factor and sensitivity are calculated.

  11. Enhancement in the interfacial perpendicular magnetic anisotropy and the voltage-controlled magnetic anisotropy by heavy metal doping at the Fe/MgO interface

    Directory of Open Access Journals (Sweden)

    Takayuki Nozaki

    2018-02-01

    Full Text Available We investigated the influence of heavy metal doping at the Fe/MgO interface on the interfacial perpendicular magnetic anisotropy (PMA and the voltage-controlled magnetic anisotropy (VCMA in magnetic tunnel junctions prepared by sputtering-based deposition. The interfacial PMA was increased by tungsten doping and a maximum intrinsic interfacial PMA energy, Ki,0 of 2.0 mJ/m2 was obtained. Ir doping led to a large increase in the VCMA coefficient by a factor of 4.7 compared with that for the standard Fe/MgO interface. The developed technique provides an effective approach to enhancing the interfacial PMA and VCMA properties in the development of voltage-controlled spintronic devices.

  12. Magnetocrystalline anisotropy and its electric-field-assisted switching of Heusler-compound-based perpendicular magnetic tunnel junctions

    International Nuclear Information System (INIS)

    Bai, Zhaoqiang; Wu, Qingyun; Zeng, Minggang; Feng, Yuan Ping; Shen, Lei; Cai, Yongqing; Han, Guchang

    2014-01-01

    Employing density functional theory combined with the non-equilibrium Green's function formalism, we systematically investigate the structural, magnetic and magnetoelectric properties of the Co 2 FeAl(CFA)/MgO interface, as well as the spin-dependent transport characteristics of the CFA/MgO/CFA perpendicular magnetic tunnel junctions (p-MTJs). We find that the structure of the CFA/MgO interface with the oxygen-top FeAl termination has high thermal stability, which is protected by the thermodynamic equilibrium limit. Furthermore, this structure is found to have perpendicular magnetocrystalline anisotropy (MCA). Giant electric-field-assisted modifications of this interfacial MCA through magnetoelectric coupling are demonstrated with an MCA coefficient of up to 10 −7 erg V −1 cm. In addition, our non-collinear spin transport calculations of the CFA/MgO/CFA p-MTJ predict a good magnetoresistance performance of the device. (paper)

  13. Exchange bias and perpendicular anisotropy study of ultrathin Pt-Co-Pt-IrMn multilayers sputtered on float glass

    Science.gov (United States)

    Laval, M.; Lüders, U.; Bobo, J. F.

    2007-09-01

    We have prepared ultrathin Pt-Co-Pt-IrMn polycrystalline multilayers on float-glass substrates by DC magnetron sputtering. We have determined the optimal set of thickness for both Pt layers, the Co layer and the IrMn biasing layer so that these samples exhibit at the same time out-of-plane magnetic anisotropy and exchange bias. Kerr microscopy domain structure imaging evidences an increase of nucleation rate accompanied with inhomogeneous magnetic behavior in the case of exchange-biased films compared to Pt-Co-Pt trilayers. Polar hysteresis loops are measured in obliquely applied magnetic field conditions, allowing us to determine both perpendicular anisotropy effective constant Keff and exchange-bias coupling JE, which are significantly different from the ones determined by standard switching field measurements.

  14. Exchange bias and perpendicular anisotropy study of ultrathin Pt-Co-Pt-IrMn multilayers sputtered on float glass

    International Nuclear Information System (INIS)

    Laval, M.; Lueders, U.; Bobo, J.F.

    2007-01-01

    We have prepared ultrathin Pt-Co-Pt-IrMn polycrystalline multilayers on float-glass substrates by DC magnetron sputtering. We have determined the optimal set of thickness for both Pt layers, the Co layer and the IrMn biasing layer so that these samples exhibit at the same time out-of-plane magnetic anisotropy and exchange bias. Kerr microscopy domain structure imaging evidences an increase of nucleation rate accompanied with inhomogeneous magnetic behavior in the case of exchange-biased films compared to Pt-Co-Pt trilayers. Polar hysteresis loops are measured in obliquely applied magnetic field conditions, allowing us to determine both perpendicular anisotropy effective constant K eff and exchange-bias coupling J E , which are significantly different from the ones determined by standard switching field measurements

  15. Voltage control of a magnetic switching field for magnetic tunnel junctions with low resistance and perpendicular magnetic anisotropy

    Science.gov (United States)

    Tezuka, N.; Oikawa, S.; Matsuura, M.; Sugimoto, S.; Nishimura, K.; Irisawa, T.; Nagamine, Y.; Tsunekawa, K.

    2018-05-01

    The authors investigated the voltage control of a magnetic anisotropy field for perpendicular-magnetic tunnel junctions (p-MTJs) with low and high resistance-area (RA) products and for synthetic antiferromagnetic free and pinned layers. It was found that the sample with low RA products was more sensitive to the applied bias voltage than the sample with high RA products. The bias voltage effect was less pronounced for our sample with the synthetic antiferromagnetic layer for high RA products compared to the MTJs with single free and pinned layers.

  16. Tunnel magnetoresistance in thermally robust Mo/CoFeB/MgO tunnel junction with perpendicular magnetic anisotropy

    Directory of Open Access Journals (Sweden)

    B. Fang

    2015-06-01

    Full Text Available We report on tunnel magnetoresistance and electric-field effect in the Mo buffered and capped CoFeB/MgO magnetic tunnel junctions (MTJs with perpendicular magnetic anisotropy. A large tunnel magnetoresistance of 120% is achieved. Furthermore, this structure shows greatly improved thermal stability and stronger electric-field-induced modulation effect in comparison with the Ta/CoFeB/MgO-based MTJs. These results suggest that the Mo-based MTJs are more desirable for next generation spintronic devices.

  17. Manipulation of perpendicular magnetic anisotropy of single Fe atom adsorbed graphene via MgO(1 1 1) substrate

    Science.gov (United States)

    Fu, Mingming; Tang, Weiqing; Wu, Yaping; Ke, Congming; Guo, Fei; Zhang, Chunmiao; Yang, Weihuang; Wu, Zhiming; Kang, Junyong

    2018-05-01

    Perpendicular magnetic anisotropy is significantly important for realizing a long-term retention of information for spintronics devices. Inspired by 2D graphene with its high charge carrier mobility and long spin diffusion length, we report a first-principles design framework on perpendicular magnetic anisotropy engineering of a Fe atom adsorbed graphene by employing a O-terminated MgO (1 1 1) substrate. Determined by the adsorption sites of the Fe atom, a tunable magnetic anisotropy is realized in Fe/graphene/MgO (1 1 1) structure, with the magnetic anisotropy energy of  ‑0.48 meV and 0.23 meV, respectively, corresponding to the in-plane and out of plane easy magnetizations. Total density of states suggest a half-metallicity with a 100% spin polarization in the system. Decomposed densities of Fe-3d states reveal the orbital contributions to the magnetic anisotropy for different Fe adsorption sites. Bonding interaction and charge redistribution regulated by MgO substrate are found responsible for the novel perpendicular magnetic anisotropy engineering in the system. The effective manipulation of perpendicular magnetic anisotropy in present work offers some references for the design and construction of 2D spintronics devices.

  18. Observation of the domain structure in Fe-Au superlattices with perpendicular anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Zoladz, M. E-mail: zoladz@uci.agh.edu.pl; Slezak, T.; Wilgocka-Slezak, D.; Spiridis, N.; Korecki, J.; Stobiecki, T. E-mail: stobieck@uci.agh.edu.pl; Roell, K

    2004-05-01

    Polar Kerr Microscopy was used to visualize characteristic transitions and external magnetic field driven domain structure evolution in a perpendicularly magnetized Fe-Au AF/FM double multilayer structure. Real time imaging performed in the external magnetic field allowed for identification of all sublayers magnetization reversal in accordance with measured PMOKE magnetization curve, showing strong dependence of transition character on the interlayer coupling type and adjacent sublayers magnetization orientation.

  19. Observation of the domain structure in Fe-Au superlattices with perpendicular anisotropy

    International Nuclear Information System (INIS)

    Zoladz, M.; Slezak, T.; Wilgocka-Slezak, D.; Spiridis, N.; Korecki, J.; Stobiecki, T.; Roell, K.

    2004-01-01

    Polar Kerr Microscopy was used to visualize characteristic transitions and external magnetic field driven domain structure evolution in a perpendicularly magnetized Fe-Au AF/FM double multilayer structure. Real time imaging performed in the external magnetic field allowed for identification of all sublayers magnetization reversal in accordance with measured PMOKE magnetization curve, showing strong dependence of transition character on the interlayer coupling type and adjacent sublayers magnetization orientation

  20. Antidot patterned single and bilayer thin films based on ferrimagnetic Tb-Co alloy with perpendicular magnetic anisotropy

    Science.gov (United States)

    Kulesh, N. A.; Vázquez, M.; Lepalovskij, V. N.; Vas'kovskiy, V. O.

    2018-02-01

    Hysteresis properties and magnetization reversal in TbCo(30 nm) and FeNi(10 nm)/TbCo(30 nm) films with nanoscale antidot lattices are investigated to test the effect of nanoholes on the perpendicular anisotropy in the TbCo layer and the induced exchange bias in the FeNi layer. The antidots are introduced by depositing the films on top of hexagonally ordered porous anodic alumina substrates with pore diameter and interpore distance fixed to 75 nm and 105 nm, respectively. The analysis of combined vibrating sample magnetometry, Kerr microscopy and magnetic force microscopy imaging measurements has allowed us to link macroscopic and local magnetization reversal processes. For magnetically hard TbCo films, we demonstrate the tunability of magnetic anisotropy and coercive field (i.e., it increases from 0.2 T for the continuous film to 0.5 T for the antidot film). For the antidot FeNi/TbCo film, magnetization of FeNi is confirmed to be in plane. Although an exchange bias has been locally detected in the FeNi layer, the integrated hysteresis loop has increased coercivity and zero shift along the field axis due to the significantly decreased magnetic anisotropy of TbCo layer.

  1. Influence of domain structure induced coupling on magnetization reversal of Co/Pt/Co film with perpendicular anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Matczak, Michał [Institute of Molecular Physics, Polish Academy of Sciences, M. Smoluchowskiego 17, 60-179 Poznań (Poland); NanoBioMedical Centre, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań (Poland); Schäfer, Rudolf [Leibniz Institute for Solid State and Materials Research (IFW) Dresden, Institute for Metallic Materials, PO 270116, D-01171 Dresden (Germany); Dresden University of Technology, Institute for Materials Science, D-01062 Dresden (Germany); Urbaniak, Maciej; Kuświk, Piotr; Szymański, Bogdan; Schmidt, Marek; Aleksiejew, Jacek [Institute of Molecular Physics, Polish Academy of Sciences, M. Smoluchowskiego 17, 60-179 Poznań (Poland); Stobiecki, Feliks, E-mail: Feliks.Stobiecki@ifmpan.poznan.pl [Institute of Molecular Physics, Polish Academy of Sciences, M. Smoluchowskiego 17, 60-179 Poznań (Poland); NanoBioMedical Centre, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań (Poland)

    2017-01-15

    A magnetic multilayer of substrate/Pt-15 nm/Co-0.8 nm/Pt-wedge 0–7 nm/Co-0.6 nm/Pt-2 nm structure is characterized by a perpendicular anisotropy of the Co layers and by graded interlayer coupling between them. Using magnetooptical Kerr microscopy we observed a distinct influence of magnetic domains in one Co layer on the nucleation field and positions of nucleation sites of reversed domains in the second Co layer. For sufficiently strong interlayer coupling a replication of magnetic domains from the magnetically harder layer to the magnetically softer layer is observed. - Highlights: • Co/Pt-wedge/Co layered film is characterized by a gradient of interlayer coupling. • Magnetic field controls propagation of straight domain wall. • Replication of magnetic domains in multilayers with strong ferromagnetic coupling. • Coupling induced by domains influences magnetization reversal of spin valves.

  2. Role of polarizer-tilting-angle in zero-field spin-transfer nano-oscillators with perpendicular anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez-Fuentes, C.; Gallardo, R. A., E-mail: rodolfo.gallardo@usm.cl; Landeros, P. [Departamento de Física, Universidad Técnica Federico Santa María, Avenida España 1680, 2390123 Valparaíso (Chile)

    2015-10-05

    An analytical model for studying the stability of a single domain ferromagnetic layer under the influence of a spin-polarized current is presented. The theory is applied to bias-field-free nano-oscillators with perpendicular anisotropy, which allows to obtain a polarizer-angle vs. current phase diagram that describes the stability of magnetic states. Explicit formulae for the critical current densities unveil the influence of the relative orientation between free and polarizer layers, allowing the emergence of precessional steady-states, and also the possibility to reduce the magnitude of the threshold current density to produce microwave oscillations. It is shown that oscillating steady-states arise in a broad angular region, and the dependence of their boundaries is fully specified by the model. The reliability of the analytical results has been corroborated by comparison to numerical calculations. Such structures are currently under intense research because of remarkable properties offering new prospects for microwave applications in communication technologies.

  3. Ta thickness-dependent perpendicular magnetic anisotropy features in Ta/CoFeB/MgO/W free layer stacks

    Energy Technology Data Exchange (ETDEWEB)

    Yang, SeungMo; Lee, JaBin; An, GwangGuk [Novel Functional Materials and Devices Lab, The Research Institute for Natural Science, Department of Physics, Hanyang University, Seoul 133-791 (Korea, Republic of); Kim, JaeHong [Division of Nano-Scale Semiconductor Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Chung, WooSeong [Nano Quantum Electronics Lab, Department of Electronics and Computer Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Hong, JinPyo, E-mail: jphong@hanyang.ac.kr [Novel Functional Materials and Devices Lab, The Research Institute for Natural Science, Department of Physics, Hanyang University, Seoul 133-791 (Korea, Republic of); Division of Nano-Scale Semiconductor Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of)

    2015-07-31

    We describe Ta underlayer thickness influence on thermal stability of perpendicular magnetic anisotropy in Ta/CoFeB/MgO/W stacks. It is believed that thermal stability based on Ta underlay is associated with thermally-activated Ta atom diffusion during annealing. The difference in Ta thickness-dependent diffusion behaviors was confirmed with X-ray photoelectron spectroscopy analysis. Along with a feasible Ta thickness model, our observations suggest that an appropriate seed layer choice is needed for high temperature annealing stability, a critical issue in the memory industry. - Highlights: • We observed changes in the diffusion behavior with regard to Ta seed layer thickness. • It was observed that a thinner Ta seed layer induced more annealing-stable features. • However, ultra-thin (0.75 nm) Ta shows unstable characteristics about the annealing process. • It was possibly due to a rugged interface of the Ta layer by the island growth process.

  4. Electric-field tunable perpendicular magnetic anisotropy in tetragonal Fe4N/BiFeO3 heterostructures

    Science.gov (United States)

    Yin, Li; Wang, Xiaocha; Mi, Wenbo

    2017-07-01

    Electric field control on perpendicular magnetic anisotropy (PMA) is indispensable for spintronic devices. Herewith, in tetragonal Fe4N/BiFeO3 heterostructures with the FeAFeB/Fe-O2 interface, PMA in each Fe4N layer, not merely interfacial layers, is modulated by the electric field, which is attributed to the broken spin screening of the electric field in highly spin-polarized Fe4N. Moreover, the periodical dx y+dy z+dz2 and dx y+dx2-y2 orbital-PMA oscillation enhances the interactions between adjacent FeAFeB and (FeB)2N atomic layers, which benefits the electric field modulation on PMA in the whole Fe4N atomic layers. The electric-field control on PMA in Fe4N/BiFeO3 heterostructures is favored by the electric-field-lifted potential in Fe4N.

  5. Study of relaxation processes and uniaxial anisotropy in the Europium Gallium Garnet epitaxial films

    International Nuclear Information System (INIS)

    Mukhopadhyay, P.

    1987-04-01

    We report here the magnetic properties of Europium-Gallium Garnet LPE films of the type Eu x Y 3-x Fe 5-y Ga y O 12 (where O< x<1.2 and 1< y<1.1). The mechanism by which the magnetic moments relax in Eu or Sm Garnets is still not fully understood. We have made studies on Eu-Ga garnet films and explain some of the results observed in these films. Pb and Pt ions are always found as impurities in our films. Pb ions contribute to the anisotropy in the film. Most of the experimental results can be explained with the three sub lattice model. The shape of the FMR line width shows strong sensitivity towards the surface impurities. (author). 18 refs, 6 figs, 1 tab

  6. Determination of perpendicular magnetic anisotropy based on the magnetic droplet nucleation

    Science.gov (United States)

    Nishimura, Tomoe; Kim, Duck-Ho; Okuno, Takaya; Hirata, Yuushou; Futakawa, Yasuhiro; Yoshikawa, Hiroki; Kim, Sanghoon; Tsukamoto, Arata; Shiota, Yoichi; Moriyama, Takahiro; Ono, Teruo

    2018-05-01

    We propose an alternative method of determining the magnetic anisotropy field μ0 H K in ferro-/ferrimagnets. On the basis of the droplet nucleation model, there exists linearity between domain-wall (DW) energy density and in-plane magnetic field. We find that the slope is simply represented by μ0 H K and Dzyaloshinskii–Moriya interaction (DMI). By measuring the in-plane magnetic field dependence of the coercivity field, closely corresponding to the DW energy density, a robust value for μ0 H K can be quantified. This robust value can be used to determine μ0 H K over a wide range of values, overcoming the limitations caused by the small strength of the external magnetic field typically used in experiments.

  7. Direct Observation of Field and Temperature Induced Domain Replication in Dipolar Coupled Perpendicular Anisotropy Films

    Energy Technology Data Exchange (ETDEWEB)

    Hauet, T.; Gunther, C.M.; Pfau, B.; Eisebitt, S.; Fischer, P.; Rick, R. L.; Thiele, J.-U.; Hellwig, O.; Schabes, M.E.

    2007-07-01

    Dipolar interactions in a soft/Pd/hard [CoNi/Pd]{sub 30}/Pd/[Co/Pd]{sub 20} multilayer system, where a thick Pd layer between two ferromagnetic units prevents direct exchange coupling, are directly revealed by combining magnetometry and state-of-the-art layer resolving soft x-ray imaging techniques with sub-100-nm spatial resolution. The domains forming in the soft layer during external magnetic field reversal are found to match the domains previously trapped in the hard layer. The low Curie temperature of the soft layer allows varying its intrinsic parameters via temperature and thus studying the competition with dipolar fields due to the domains in the hard layer. Micromagnetic simulations elucidate the role of [CoNi/Pd] magnetization, exchange, and anisotropy in the duplication process. Finally, thermally driven domain replication in remanence during temperature cycling is demonstrated.

  8. Termination layer compensated tunnelling magnetoresistance in ferrimagnetic Heusler compounds with high perpendicular magnetic anisotropy.

    Science.gov (United States)

    Jeong, Jaewoo; Ferrante, Yari; Faleev, Sergey V; Samant, Mahesh G; Felser, Claudia; Parkin, Stuart S P

    2016-01-18

    Although high-tunnelling spin polarization has been observed in soft, ferromagnetic, and predicted for hard, ferrimagnetic Heusler materials, there has been no experimental observation to date of high-tunnelling magnetoresistance in the latter. Here we report the preparation of highly textured, polycrystalline Mn3Ge films on amorphous substrates, with very high magnetic anisotropy fields exceeding 7 T, making them technologically relevant. However, the small and negative tunnelling magnetoresistance that we find is attributed to predominant tunnelling from the lower moment Mn-Ge termination layers that are oppositely magnetized to the higher moment Mn-Mn layers. The net spin polarization of the current reflects the different proportions of the two distinct termination layers and their associated tunnelling matrix elements that result from inevitable atomic scale roughness. We show that by engineering the spin polarization of the two termination layers to be of the same sign, even though these layers are oppositely magnetized, high-tunnelling magnetoresistance is possible.

  9. Growth and characterization of MnGa thin films with perpendicular magnetic anisotropy on BiSb topological insulator

    Science.gov (United States)

    Duy Khang, Nguyen Huynh; Ueda, Yugo; Yao, Kenichiro; Hai, Pham Nam

    2017-10-01

    We report on the crystal growth as well as the structural and magnetic properties of Bi0.8Sb0.2 topological insulator (TI)/MnxGa1-x bi-layers grown on GaAs(111)A substrates by molecular beam epitaxy. By optimizing the growth conditions and Mn composition, we were able to grow MnxGa1-x thin films on Bi0.8Sb0.2 with the crystallographic orientation of Bi0.8Sb0.2(001)[1 1 ¯ 0]//MnGa (001)[100]. Using magnetic circular dichroism (MCD) spectroscopy, we detected both the L10 phase ( x 0.6 ) of MnxGa1-x. For 0.50 ≤ x ≤ 0.55 , we obtained ferromagnetic L10-MnGa thin films with clear perpendicular magnetic anisotropy, which were confirmed by MCD hysteresis, anomalous Hall effect as well as superconducting quantum interference device measurements. Our results show that the BiSb/MnxGa1-x bi-layer system is promising for perpendicular magnetization switching using the giant spin Hall effect in TIs.

  10. Thick CoFeB with perpendicular magnetic anisotropy in CoFeB-MgO based magnetic tunnel junction

    Directory of Open Access Journals (Sweden)

    V. B. Naik

    2012-12-01

    Full Text Available We have investigated the effect of an ultra-thin Ta insertion in the CoFeB (CoFeB/Ta/CoFeB free layer (FL on magnetic and tunneling magnetoresistance (TMR properties of a CoFeB-MgO system with perpendicular magnetic anisotropy (PMA. It is found that the critical thickness (tc to sustain PMA is doubled (tc = 2.6 nm in Ta-inserted CoFeB FL as compared to single CoFeB layer (tc = 1.3 nm. While the effective magnetic anisotropy is found to increase with Ta insertion, the saturation magnetization showed a slight reduction. As the CoFeB thickness increasing, the thermal stability of Ta inserted structure is significantly increased by a factor of 2.5 for total CoFeB thickness less than 2 nm. We have observed a reasonable value of TMR for a much thicker CoFeB FL (thickness = 2-2.6 nm with Ta insertion, and without significant increment in resistance-area product. Our results reveal that an ultra-thin Ta insertion in CoFeB might pay the way towards developing the high-density memory devices with enhanced thermal stability.

  11. Dual-mode ferromagnetic resonance in an FeCoB/Ru/FeCoB synthetic antiferromagnet with uniaxial anisotropy

    Science.gov (United States)

    Wang, Cuiling; Zhang, Shouheng; Qiao, Shizhu; Du, Honglei; Liu, Xiaomin; Sun, Ruicong; Chu, Xian-Ming; Miao, Guo-Xing; Dai, Youyong; Kang, Shishou; Yan, Shishen; Li, Shandong

    2018-05-01

    Dual-mode ferromagnetic resonance is observed in FeCoB/Ru/FeCoB trilayer synthetic antiferromagnets with uniaxial in-plane magnetic anisotropy. The optical mode is present in the (0-108 Oe) magnetic field range, where the top and bottom layer magnetizations are aligned in opposite directions. The strong acoustic mode appears, when the magnetic field exceeds the 300 Oe value, which corresponds to the flop transition in the trilayer. Magnetic field and angular dependences of resonant frequencies are studied for both optical (low-field) and acoustic (high field) modes. The low-field mode is found to be anisotropic but insensitive to the magnetic field value. In contrast, the high field mode is quasi-isotropic, but its resonant frequency is tunable by the value of the magnetic field. The coexistence of two modes of ferromagnetic resonance as well as switching between them with the increase in the magnetic field originates from the difference in the sign of interlayer coupling energy at the parallel and antiparallel configurations of the synthetic antiferromagnet. The dual-mode resonance in the studied trilayer structures provides greater flexibility in the design and functionalization of micro-inductors in monolithic microwave integrated circuits.

  12. Observation of Various and Spontaneous Magnetic Skyrmionic Bubbles at Room Temperature in a Frustrated Kagome Magnet with Uniaxial Magnetic Anisotropy

    KAUST Repository

    Hou, Zhipeng

    2017-06-07

    The quest for materials hosting topologically protected skyrmionic spin textures continues to be fueled by the promise of novel devices. Although many materials have demonstrated the existence of such spin textures, major challenges remain to be addressed before devices based on magnetic skyrmions can be realized. For example, being able to create and manipulate skyrmionic spin textures at room temperature is of great importance for further technological applications because they can adapt to various external stimuli acting as information carriers in spintronic devices. Here, the first observation of skyrmionic magnetic bubbles with variable topological spin textures formed at room temperature in a frustrated kagome Fe3 Sn2 magnet with uniaxial magnetic anisotropy is reported. The magnetization dynamics are investigated using in situ Lorentz transmission electron microscopy, revealing that the transformation between different magnetic bubbles and domains is via the motion of Bloch lines driven by an applied external magnetic field. These results demonstrate that Fe3 Sn2 facilitates a unique magnetic control of topological spin textures at room temperature, making it a promising candidate for further skyrmion-based spintronic devices.

  13. In-plane current induced domain wall nucleation and its stochasticity in perpendicular magnetic anisotropy Hall cross structures

    International Nuclear Information System (INIS)

    Sethi, P.; Murapaka, C.; Lim, G. J.; Lew, W. S.

    2015-01-01

    Hall cross structures in magnetic nanowires are commonly used for electrical detection of magnetization reversal in which a domain wall (DW) is conventionally nucleated by a local Oersted field. In this letter, we demonstrate DW nucleation in Co/Ni perpendicular magnetic anisotropy nanowire at the magnetic Hall cross junction. The DWs are nucleated by applying an in-plane pulsed current through the nanowire without the need of a local Oersted field. The change in Hall resistance, detected using anomalous Hall effect, is governed by the magnetic volume switched at the Hall junction, which can be tuned by varying the magnitude of the applied current density and pulse width. The nucleated DWs are driven simultaneously under the spin transfer torque effect when the applied current density is above a threshold. The possibility of multiple DW generation and variation in magnetic volume switched makes nucleation process stochastic in nature. The in-plane current induced stochastic nature of DW generation may find applications in random number generation

  14. Tailoring of Perpendicular Magnetic Anisotropy in Dy13Fe87 Thin Films with Hexagonal Antidot Lattice Nanostructure

    Directory of Open Access Journals (Sweden)

    Mohamed Salaheldeen

    2018-04-01

    Full Text Available In this article, the magnetic properties of hexagonally ordered antidot arrays made of Dy13Fe87 alloy are studied and compared with corresponding ones of continuous thin films with the same compositions and thicknesses, varying between 20 nm and 50 nm. Both samples, the continuous thin films and antidot arrays, were prepared by high vacuum e-beam evaporation of the alloy on the top-surface of glass and hexagonally self-ordered nanoporous alumina templates, which serve as substrates, respectively. By using a highly sensitive magneto-optical Kerr effect (MOKE and vibrating sample magnetometer (VSM measurements an interesting phenomenon has been observed, consisting in the easy magnetization axis transfer from a purely in-plane (INP magnetic anisotropy to out-of-plane (OOP magnetization. For the 30 nm film thickness we have measured the volume hysteresis loops by VSM with the easy magnetization axis lying along the OOP direction. Using magnetic force microscopy measurements (MFM, there is strong evidence to suggest that the formation of magnetic domains with OOP magnetization occurs in this sample. This phenomenon can be of high interest for the development of novel magnetic and magneto-optic perpendicular recording patterned media based on template-assisted deposition techniques.

  15. Chromium-induced ferromagnetism with perpendicular anisotropy in topological crystalline insulator SnTe (111) thin films

    Science.gov (United States)

    Wang, Fei; Zhang, Hongrui; Jiang, Jue; Zhao, Yi-Fan; Yu, Jia; Liu, Wei; Li, Da; Chan, Moses H. W.; Sun, Jirong; Zhang, Zhidong; Chang, Cui-Zu

    2018-03-01

    Topological crystalline insulator is a recently discovered topological phase of matter. It possesses multiple Dirac surface states, which are protected by the crystal symmetry. This is in contrast to the time-reversal symmetry that is operative in the well-known topological insulators. In the presence of a Zeeman field and/or strain, the multiple Dirac surface states are gapped. The high-Chern-number quantum anomalous Hall (QAH) state is predicted to emerge if the chemical potential resides in all the Zeeman gaps. Here, we use molecular-beam epitaxy to grow 12 double-layer (DL) pure and Cr-doped SnTe (111) thin film on heat-treated SrTi O3 (111) substrate using a quintuple layer of insulating (Bi0.2Sb0.8 ) 2T e3 topological insulator as a buffer film. The Hall traces of Cr-doped SnTe film at low temperatures display square hysteresis loops indicating long-range ferromagnetic order with perpendicular anisotropy. The Curie temperature of the 12 DL S n0.9C r0.1Te film is ˜110 K. Due to the chemical potential crossing the bulk valence bands, the anomalous Hall resistance of 12 DL S n0.9C r0.1Te film is substantially lower than the predicted quantized value (˜1 /4 h /e2 ). It is possible that with systematic tuning the chemical potential via chemical doping and electrical gating, the high-Chern-number QAH state can be realized in the Cr-doped SnTe (111) thin film.

  16. Observation of Various and Spontaneous Magnetic Skyrmionic Bubbles at Room Temperature in a Frustrated Kagome Magnet with Uniaxial Magnetic Anisotropy

    KAUST Repository

    Hou, Zhipeng; Ren, Weijun; Ding, Bei; Xu, Guizhou; Wang, Yue; Yang, Bing; Zhang, Qiang; Zhang, Ying; Liu, Enke; Xu, Feng; Wang, Wenhong; Wu, Guangheng; Zhang, Xixiang; Shen, Baogen; Zhang, Zhidong

    2017-01-01

    to various external stimuli acting as information carriers in spintronic devices. Here, the first observation of skyrmionic magnetic bubbles with variable topological spin textures formed at room temperature in a frustrated kagome Fe3 Sn2 magnet with uniaxial

  17. Perpendicular magnetic anisotropy in Ta|Co40Fe40B20|MgAl2O4 structures and perpendicular CoFeB|MgAl2O4|CoFeB magnetic tunnel junction

    KAUST Repository

    Tao, B. S.

    2014-09-08

    Magnetic properties of Co40Fe40B20(CoFeB) thin films sandwiched between Ta and MgAl2O4layers have been systematically studied. For as-grown state, Ta/CoFeB/MgAl2O4structures exhibit good perpendicular magnetic anisotropy (PMA) with interface anisotropy Ki=1.22erg/cm2, which further increases to 1.30erg/cm2after annealing, while MgAl2O4/CoFeB/Ta multilayer shows in-plane magnetic anisotropy and must be annealed in order to achieve PMA. For bottom CoFeB layer, the thickness window for PMA is from 0.6 to 1.0nm, while that for top CoFeB layer is between 0.8 and 1.4nm. Perpendicular magnetic tunnel junctions (p-MTJs) with a core structure of CoFeB/MgAl2O4/CoFeB have also been fabricated and tunneling magnetoresistance ratio of about 36% at room temperature and 63% at low temperature have been obtained. The intrinsic excitations in the p-MTJs have been identified by inelastic electron-tunneling spectroscopy.

  18. Perpendicular magnetic anisotropy in Ta|Co40Fe40B20|MgAl2O4 structures and perpendicular CoFeB|MgAl2O4|CoFeB magnetic tunnel junction

    KAUST Repository

    Tao, B. S.; Li, D. L.; Yuan, Z. H.; Liu, H. F.; Ali, S. S.; Feng, J. F.; Wei, H. X.; Han, X. F.; Liu, Y.; Zhao, Y. G.; Zhang, Q.; Guo, Zaibing; Zhang, Xixiang

    2014-01-01

    Magnetic properties of Co40Fe40B20(CoFeB) thin films sandwiched between Ta and MgAl2O4layers have been systematically studied. For as-grown state, Ta/CoFeB/MgAl2O4structures exhibit good perpendicular magnetic anisotropy (PMA) with interface anisotropy Ki=1.22erg/cm2, which further increases to 1.30erg/cm2after annealing, while MgAl2O4/CoFeB/Ta multilayer shows in-plane magnetic anisotropy and must be annealed in order to achieve PMA. For bottom CoFeB layer, the thickness window for PMA is from 0.6 to 1.0nm, while that for top CoFeB layer is between 0.8 and 1.4nm. Perpendicular magnetic tunnel junctions (p-MTJs) with a core structure of CoFeB/MgAl2O4/CoFeB have also been fabricated and tunneling magnetoresistance ratio of about 36% at room temperature and 63% at low temperature have been obtained. The intrinsic excitations in the p-MTJs have been identified by inelastic electron-tunneling spectroscopy.

  19. Perpendicular magnetic anisotropy in Co2FeAl0.5Si0.5/MgO bottom electrodes for magnetic tunnel junctions

    International Nuclear Information System (INIS)

    Li, X.Q.; Wu, Y.; Gao, S.; Xu, X.G.; Miao, J.; Jiang, Y.

    2013-01-01

    Perpendicular magnetic anisotropy (PMA) was achieved in annealed Co 2 FeAl 0.5 Si 0.5 (CFAS)/MgO-based multilayers with good thermal stability up to 400 °C and a large anisotropy energy density K u over 2.0 × 10 5 J/m 3 . The thickness of the full-Heusler CFAS film to maintain PMA is up to 4.8 nm in which the co-existence of disordered A2, ordered B2 and fully ordered L2 1 structures is observed. X-ray photoelectron spectroscopy analysis demonstrates that the origin of the PMA is the hybridization between Co 3d and O 2p orbitals at the CFAS/MgO interface. - Highlights: • We achieved perpendicular magnetic anisotropy (PMA) in Co 2 FeAl 0.5 Si 0.5 (4.8 nm) film; • L2 1 , B2 and A2 phases coexist in perpendicular magnetic anisotropic Co 2 FeAl 0.5 Si 0.5 ; • Magnetic properties have strong dependence on the annealing temperature; • The PMA is induced by the hybridization between Co-3d and O-2p orbitals

  20. Depth-Dependent Anisotropies of Amides and Sugar in Perpendicular and Parallel Sections of Articular Cartilage by Fourier Transform Infrared Imaging (FTIRI)

    Science.gov (United States)

    Xia, Yang; Mittelstaedt, Daniel; Ramakrishnan, Nagarajan; Szarko, Matthew; Bidthanapally, Aruna

    2010-01-01

    Full thickness blocks of canine humeral cartilage were microtomed into both perpendicular sections and a series of 100 parallel sections, each 6 μm thick. Fourier Transform Infrared Imaging (FTIRI) was used to image each tissue section eleven times under different infrared polarizations (from 0° to 180° polarization states in 20° increments and with an additional 90° polarization), at a spatial resolution of 6.25 μm and a wavenumber step of 8 cm−1. With increasing depth from the articular surface, amide anisotropies increased in the perpendicular sections and decreased in the parallel sections. Both types of tissue sectioning identified a 90° difference between amide I and amide II in the superficial zone of cartilage. The fibrillar distribution in the parallel sections from the superficial zone was shown to not be random. Sugar had the greatest anisotropy in the upper part of the radial zone in the perpendicular sections. The depth-dependent anisotropic data were fitted with a theoretical equation that contained three signature parameters, which illustrate the arcade structure of collagens with the aid of a fibril model. Infrared imaging of both perpendicular and parallel sections provides the possibility of determining the three-dimensional macromolecular structures in articular cartilage. Being sensitive to the orientation of the macromolecular structure in healthy articular cartilage aids the prospect of detecting the early onset of the tissue degradation that may lead to pathological conditions such as osteoarthritis. PMID:21274999

  1. Exchange bias energy in Co/Pt/IrMn multilayers with perpendicular and in-plane anisotropy

    International Nuclear Information System (INIS)

    Czapkiewicz, M.; Stobiecki, T.; Rak, R.; Zoladz, M.; Dijken, S. van

    2007-01-01

    The magnetization reversal process in perpendicularly biased [Pt/Co] 3 /d Pt Pt/IrMn and in-plane biased Co/d Pt Pt/IrMn multilayers with 0nm= Pt = Pt =0.1nm. In both cases, the existence of large exchange bias fields correlates with a high domain density during magnetization reversal. The interface exchange coupling energy is larger for the in-plane biased films than for the perpendicularly biased multilayers

  2. The resonance susceptibility of two-layer exchange-coupled ferromagnetic film with a combined uniaxial and cubic anisotropy in the layers

    Energy Technology Data Exchange (ETDEWEB)

    Shul’ga, N.V., E-mail: shulga@anrb.ru; Doroshenko, R.A.

    2016-12-01

    A numerical investigation of the resonance dynamic susceptibility of ferromagnetic exchange-coupled two-layer films with a combined cubic and uniaxial magnetic anisotropy of the layers has been performed. It has been found that the presence of cubic anisotropy leads to the fact that much of the off-diagonal components of the dynamic susceptibility are nonzero. The change of the ferromagnetic resonance frequencies and dynamic susceptibility upon the magnetization along the [100], [010], and [011] directions have been calculated. The evolution of the profile of the dynamic susceptibility occurring during the magnetization has been described. The impact of changes in the distribution of equilibrium and dynamic components of the magnetization on the dependences of the components of the dynamic susceptibility and the ferromagnetic resonance frequency on the external magnetic fields has been discussed. - Highlights: • The extremes in the dependences of integrated dynamic susceptibility components are observed at low fields. • Lower extremes can be observed at a shift of the localization of the lower FMR mode toward the interface between the layers. • The features of the distribution of the dynamic susceptibility over the thickness have been discussed. • The cubic anisotropy leads to the fact that the off-diagonal integrated dynamic susceptibility components are essential. • FMR signal can be excited in vicinity of the interlayer boundary.

  3. First-principles investigation of the very large perpendicular magnetic anisotropy at Fe | MgO and Co | MgO interfaces

    KAUST Repository

    Yang, H. X.; Chshiev, M.; Dieny, B.; Lee, J. H.; Manchon, Aurelien; Shin, K. H.

    2011-01-01

    The perpendicular magnetic anisotropy (PMA) arising at the interface between ferromagnetic transition metals and metallic oxides was investigated via first-principles calculations. In this work very large values of PMA, up to 3 erg/cm2, at Fe|MgO interfaces are reported, in agreement with recent experiments. The origin of PMA is attributed to overlap between O-pz and transition metal dz2 orbitals hybridized with dxz(yz) orbitals with stronger spin-orbit coupling-induced splitting around the Fermi level for perpendicular magnetization orientation. Furthermore, it is shown that the PMA value weakens in the case of over- or underoxidation due to the fact that oxygen pz and transition metal dz2 orbital overlap is strongly affected by disorder, in agreement with experimental observations in magnetic tunnel junctions.

  4. First-principles investigation of the very large perpendicular magnetic anisotropy at Fe | MgO and Co | MgO interfaces

    KAUST Repository

    Yang, H. X.

    2011-08-01

    The perpendicular magnetic anisotropy (PMA) arising at the interface between ferromagnetic transition metals and metallic oxides was investigated via first-principles calculations. In this work very large values of PMA, up to 3 erg/cm2, at Fe|MgO interfaces are reported, in agreement with recent experiments. The origin of PMA is attributed to overlap between O-pz and transition metal dz2 orbitals hybridized with dxz(yz) orbitals with stronger spin-orbit coupling-induced splitting around the Fermi level for perpendicular magnetization orientation. Furthermore, it is shown that the PMA value weakens in the case of over- or underoxidation due to the fact that oxygen pz and transition metal dz2 orbital overlap is strongly affected by disorder, in agreement with experimental observations in magnetic tunnel junctions.

  5. Perpendicular magnetic anisotropy at the interface between ultrathin Fe film and MgO studied by angular-dependent x-ray magnetic circular dichroism

    Energy Technology Data Exchange (ETDEWEB)

    Okabayashi, J. [Research Center for Spectrochemistry, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033 (Japan); Koo, J. W.; Mitani, S. [National Institute for Materials Science (NIMS), Tsukuba 305-0047 (Japan); Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8577 (Japan); Sukegawa, H. [National Institute for Materials Science (NIMS), Tsukuba 305-0047 (Japan); Takagi, Y.; Yokoyama, T. [Institute of Molecular Science, Okazaki, Aichi 444-8585 (Japan)

    2014-09-22

    Interface perpendicular magnetic anisotropy (PMA) in ultrathin Fe/MgO (001) has been investigated using angular-dependent x-ray magnetic circular dichroism (XMCD). We found that anisotropic orbital magnetic moments deduced from the analysis of XMCD contribute to the large PMA energies, whose values depend on the annealing temperature. The large PMA energies determined from magnetization measurements are related to those estimated from the XMCD and the anisotropic orbital magnetic moments through the spin-orbit interaction. The enhancement of anisotropic orbital magnetic moments can be explained mainly by the hybridization between the Fe 3d{sub z}{sup 2} and O 2p{sub z} states.

  6. Interactions controlled evolution of complex magnetoresistance in as-deposited Ag100−xCox nanogranular films with perpendicular magnetic anisotropy

    International Nuclear Information System (INIS)

    Kumar, Dinesh; Chaudhary, Sujeet; Pandya, Dinesh K.

    2015-01-01

    Evolution of a complex magnetoresistance and dc-magnetization behavior of as-deposited co-sputtered Ag 100−x Co x films with the variation of cobalt concentration ‘x’ from 25.2 to 45.1 at% is presented. At 20 K, a transition from normal to complex magnetoresistance behavior, in conjunction with magnetic force microscopy evidence of the existence of a magnetic microstructure resulting in perpendicular magnetic anisotropy (PMA) is observed for x=32.6 cobalt concentration film. The dc-magnetization studies provide additional support to the presence of PMA in film that gets reduced with the increase of cobalt concentration. The complex magnetoresistance (MR) behavior also decreases with the increase of ‘x’. The room temperature MR, coercivity behavior and remanence to saturation magnetization ratio indicate the presence of direct ferromagnetic interactions due to the presence of ferromagnetic particles for x≥32.6 films. The observed complex MR behavior and presence of PMA are interpreted in terms of manifestation of the transition of interparticle magnetic interaction nature from dipolar to direct ferromagnetic. - Highlights: • Complex MR with perpendicular magnetic anisotropy (PMA) is observed. • MFM evidenced the presence of PMA. • Complex MR and PMA decreases with the increase of cobalt concentration. • Observed results are correlated with the nature of magnetic interactions

  7. Surface-termination-dependent magnetism and strong perpendicular magnetocrystalline anisotropy of an FeRh(001) thin film

    Czech Academy of Sciences Publication Activity Database

    Jekal, S.; Rhim, S.H.; Hong, S.C.; Son, W.-J.; Shick, Alexander

    2015-01-01

    Roč. 92, č. 6 (2015), " 064410-1"-" 064410-6" ISSN 1098-0121 R&D Projects: GA ČR GA15-07172S Institutional support: RVO:68378271 Keywords : magnetic anisotropy * magnetic recording * surface science Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.736, year: 2014

  8. Perpendicular magnetic anisotropy of non-epitaxial hexagonal Co{sub 50}Pt{sub 50} thin films prepared at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, F.T., E-mail: ftyuan@gmail.com [iSentek Ltd., Advanced Sensor Laboratory, New Taipei City 22101, Taiwan (China); Chang, H.W., E-mail: wei0208@gmail.com [Department of Applied Physics, Tunghai University, Taichung 40704, Taiwan (China); Lee, P.Y.; Chang, C.Y. [Department of Applied Physics, Tunghai University, Taichung 40704, Taiwan (China); Chi, C.C. [Department of Materials Sciences and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Ouyang, H., E-mail: houyang@mx.nthu.edu.tw [Department of Materials Sciences and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan (China)

    2015-04-15

    Highlights: • In this paper, we propose a non-epitaxially grown PMA thin film of disorder hexagonal Co{sub 50}Pt{sub 50} which can satisfy all the requirements at once. • Although the preparation temperature is at room temperature and no post annealing is required, the film also shows good thermal stability up to 400 °C. • Moreover, the easy-controlling single layer deposition process of the film largely enhances the feasibility of practical production. • Significant PMA is achieved in a wide range of film thickness from 2 nm to 20 nm, which expands the usage form a GMR or TMR magnetic junctions to perpendicular spin polarizer for spin current related engineering. • The presented results may open new opportunities for advanced spintronic devices. - Abstract: Non-epitaxially induced perpendicular magnetic anisotropy (PMA) of Co{sub 50}Pt{sub 50} thin films at room temperature (RT) is reported. The CoPt film having a disordered hcp structure shows a magnetocrystalline anisotropy (K{sub u}{sup RT}) of 1–2 × 10{sup 6} erg/cm{sup 3} in a wide range of layer thickness from 2 to 20 nm. K{sub u}{sup RT} of about 1 × 10{sup 6} erg/cm{sup 3} can be preserved after a 400 °C-thermal cycle in the 5-nm-thick sample. Moderate PMA, large thickness range, simple preparation process, low formation temperature but good thermal stability make presented hcp CoPt become a remarkable option for advanced spintronic devices.

  9. Controlling magnetic domain wall motion in the creep regime in He+-irradiated CoFeB/MgO films with perpendicular anisotropy

    International Nuclear Information System (INIS)

    Herrera Diez, L.; García-Sánchez, F.; Adam, J.-P.; Devolder, T.; Eimer, S.; El Hadri, M. S.; Ravelosona, D.; Lamperti, A.; Mantovan, R.; Ocker, B.

    2015-01-01

    This study presents the effective tuning of perpendicular magnetic anisotropy in CoFeB/MgO thin films by He + ion irradiation and its effect on domain wall motion in a low field regime. Magnetic anisotropy and saturation magnetisation are found to decrease as a function of the irradiation dose which can be related to the observed irradiation-induced changes in stoichiometry at the CoFeB/MgO interface. These changes in the magnetic intrinsic properties of the film are reflected in the domain wall dynamics at low magnetic fields (H) where irradiation is found to induce a significant decrease in domain wall velocity (v). For all irradiation doses, domain wall velocities at low fields are well described by a creep law, where Ln(v) vs. H −1∕4 behaves linearly, up to a maximum field H*, which has been considered as an approximation to the value of the depinning field H dep . In turn, H* ≈ H dep is seen to increase as a function of the irradiation dose, indicating an irradiation-induced extension of the creep regime of domain wall motion

  10. Current induced multi-mode propagating spin waves in a spin transfer torque nano-contact with strong perpendicular magnetic anisotropy

    Science.gov (United States)

    Mohseni, S. Morteza; Yazdi, H. F.; Hamdi, M.; Brächer, T.; Mohseni, S. Majid

    2018-03-01

    Current induced spin wave excitations in spin transfer torque nano-contacts are known as a promising way to generate exchange-dominated spin waves at the nano-scale. It has been shown that when these systems are magnetized in the film plane, broken spatial symmetry of the field around the nano-contact induced by the Oersted field opens the possibility for spin wave mode co-existence including a non-linear self-localized spin-wave bullet and a propagating mode. By means of micromagnetic simulations, here we show that in systems with strong perpendicular magnetic anisotropy (PMA) in the free layer, two propagating spin wave modes with different frequency and spatial distribution can be excited simultaneously. Our results indicate that in-plane magnetized spin transfer nano-contacts in PMA materials do not host a solitonic self-localized spin-wave bullet, which is different from previous studies for systems with in plane magnetic anisotropy. This feature renders them interesting for nano-scale magnonic waveguides and crystals since magnon transport can be configured by tuning the applied current.

  11. Controlling magnetic domain wall motion in the creep regime in He{sup +}-irradiated CoFeB/MgO films with perpendicular anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Herrera Diez, L., E-mail: liza.herrera-diez@ief.u-psud.fr; García-Sánchez, F.; Adam, J.-P.; Devolder, T.; Eimer, S.; El Hadri, M. S.; Ravelosona, D. [Institut d' Electronique Fondamentale, Université Paris-Sud, UMR CNRS 8622, 91405 Orsay (France); Lamperti, A.; Mantovan, R. [Laboratorio MDM, IMM-CNR, Via C. Olivetti 2, 20864 Agrate (MB) (Italy); Ocker, B. [Singulus Technology AG, Hanauer Landstrasse 103, 63796 Kahl am Main (Germany)

    2015-07-20

    This study presents the effective tuning of perpendicular magnetic anisotropy in CoFeB/MgO thin films by He{sup +} ion irradiation and its effect on domain wall motion in a low field regime. Magnetic anisotropy and saturation magnetisation are found to decrease as a function of the irradiation dose which can be related to the observed irradiation-induced changes in stoichiometry at the CoFeB/MgO interface. These changes in the magnetic intrinsic properties of the film are reflected in the domain wall dynamics at low magnetic fields (H) where irradiation is found to induce a significant decrease in domain wall velocity (v). For all irradiation doses, domain wall velocities at low fields are well described by a creep law, where Ln(v) vs. H{sup −1∕4} behaves linearly, up to a maximum field H*, which has been considered as an approximation to the value of the depinning field H{sub dep}. In turn, H* ≈ H{sub dep} is seen to increase as a function of the irradiation dose, indicating an irradiation-induced extension of the creep regime of domain wall motion.

  12. Influence of Pt thickness on magnetization reversal processes in (Pt/Co)3 multilayers with perpendicular anisotropy

    International Nuclear Information System (INIS)

    Belhi, R.; Adanlété Adjanoh, A.; Vogel, J.

    2012-01-01

    We present a detailed study of the magnetization reversal in perpendicularly magnetized (Pt/Co) 3 multilayers with different values of the platinum interlayer thickness t Pt . To study the magnetization reversal in our samples we combined measurements of relaxation curves with the direct visualization of domain structures. Magnetization reversal was dominated by domain wall propagation for t Pt =1 nm and by domain nucleation for t Pt =0.2 nm, while a mixed process was observed for t Pt =0.8 nm. We interpret our results within the framework of a model of thermally activated reversal where a distribution of activation energy barriers is taken into account. The reversal process was correlated with the energy barrier distribution. - Highlights: ► We show that the coercivity decreases with the Pt interlayer thickness. ► The reversal process is sensitively dependent on platinum interlayer thickness. ► We interpreted the results by taking into account of an energy barrier distribution. ► The reversal process was correlated with the energy barrier distribution width. ► The energy barrier distribution width varies linearly with the applied field.

  13. Gigantic perpendicular magnetic anisotropy of heavy transition metal cappings on Fe/MgO(0 0 1)

    Science.gov (United States)

    Taivansaikhan, P.; Odkhuu, D.; Rhim, S. H.; Hong, S. C.

    2017-11-01

    Effects of capping layer by 5d transition metals (TM = Hf, Ta, W, Re, Os, Ir, Pt, and Au) on Fe/MgO(0 0 1), a typical magnetic tunneling junction, are systematically investigated using first-principles calculation for magnetism and magnetocrystalline-anisotropy (MCA). The early TMs having less than half-filled d bands favor magnetization antiparallel to Fe, whereas the late TMs having more than half-filled d bands favor parallel, which is explained in the framework of kinetic exchange energy. The Os capping, isovalent to Fe, enhances MCA significantly to gigantic energy of +11.31 meV/cell, where positive contribution is mostly from the partially filled majority d bands of magnetic quantum number of |m| = 1 along with stronger spin-orbit coupling of Os than Fe. Different TM cappings give different MCA energies as the Fermi level shifts according to the valence of TM: Re and Ir, just one valence more or less than Os, have still large PMCA but smaller than the Os. In the W and Pt cappings, valence difference by two, PMCA are further reduced; MCAs are lowered compared to Fe/MgO(0 0 1) by the cappings of the very early TMs (Hf and Ta), while the very late TM (Au) switches sign to in-plane MCA.

  14. 3D and 1D calculation of hysteresis loops and energy products for anisotropic nanocomposite films with perpendicular anisotropy

    International Nuclear Information System (INIS)

    Yuan, X.H.; Zhao, G.P.; Yue, Ming; Ye, L.N.; Xia, J.; Zhang, X.C.; Chang, J.

    2013-01-01

    In this paper, the magnetic reversal process, hysteresis loops and energy products for exchange-coupled Nd 2 Fe 14 B/α-Fe bilayers are studied systematically by a three-dimensional (3D) model. The 3D calculations are numerically solved using the finite difference method, where the results are carefully compared with those calculated by one-dimensional (1D) model. It is found that the calculated hysteresis loops and energy products based on the two methods are consistent with each other. Both nucleation fields and coercivities decrease monotonically as the soft layer thickness L s increases. In addition, the calculated spatial distributions of magnetization orientations in the thickness direction at various applied fields based on both methods signify a three-step magnetic reversal process, which are nucleation, growth and displacement of the domain wall. The calculated magnetic orientations within the film plane, however, are totally different according to the two methods. The 3D calculation exhibits a process of vortex formation and annihilation. On the other hand, the 1D calculation gives a quasi-coherent one, where magnetization orientation is coherent in the film plane and varies in the thickness direction. This new reversal mechanism displayed in the film plane has a systematic influence on the nucleation fields, coercivity and energy products. - Highlights: • Consistent hysteresis loops and energy products for 3D and 1D calculation. • Domain wall formation, evolution and displacement perpendicular to the film plane. • Vortex formation, annihilation and better loop squareness in 3D calculation. • Larger nucleation fields, remanence and smaller coercivity in 3D calculation

  15. High thermal stability in W/MgO/CoFeB/W/CoFeB/W stacks via ultrathin W insertion with perpendicular magnetic anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yi; Yu, Tao [School of Physics and Nuclear Energy Engineering, Beihang University, Beijing 100191 (China); Zhu, Zhengyong; Zhong, Huicai [Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029 (China); Khamis, Khamis Masoud [School of Physics and Nuclear Energy Engineering, Beihang University, Beijing 100191 (China); Zhu, Kaigui, E-mail: kgzhu@buaa.edu.cn [School of Physics and Nuclear Energy Engineering, Beihang University, Beijing 100191 (China); Key Laboratory of Micro-Nano Measurement-Manipulation and Physics, Ministry of Education, Beihang University, Beijing 100191 (China)

    2016-07-15

    The perpendicular magnetic anisotropy (PMA) of a series of top MgO/CoFeB/W stacks were studied. In these stacks, the thickness of CoFeB is limited in a range of 1.1–2.2 nm. It was found that the stack can still maintain PMA in a 1.9 nm thick CoFeB free layer. Besides, we investigated the thermal stability factor ∆ of a spin transfer torque magnetic random access memory (STT-MRAM) by inserting an ultra-thin W film of 0.8 nm between two CoFeB films. The result shows a clear PMA behavior for the samples with CoFeB thickness up to 2.5 nm, and an in-plane magnetic anisotropy (IMA) when the CoFeB is thicker than 2.5 nm. Moreover, the thermal stability factor ∆ of the CoFeB stack with W insertion is about 132 for a 50 nm size STT-MRAM device, which is remarkably improved compared to 112 for a sample without W insertion. Our results represent an alternative way to realize the endurance at high annealing temperature, high-density and high ∆ in STT-MRAM device by ultra-thin W insertion. - Highlights: • The MgO/CoFeB/W multilayer can still maintain PMA in a CoFeB thickness of 1.9 nm. • The sample with 2.5 nm thickness of CoFeB by W insertion can still maintain PMA. • The sample with W insertion can still maintain PMA until the annealing temperature as high as 350 °C. • The thermal stability factor ∆ of sample with W insertion could be increase to about 132 for a 50 nm size STT-MRAM device.

  16. Microstructural and domain effects in epitaxial CoFe2O4 films on MgO with perpendicular magnetic anisotropy

    International Nuclear Information System (INIS)

    Comes, Ryan; Gu Man; Khokhlov, Mikhail; Lu Jiwei; Wolf, Stuart A.

    2012-01-01

    CoFe 2 O 4 (CFO) epitaxial thin films of various thicknesses were grown on MgO substrates using the pulsed electron-beam deposition technique. The films have excellent in-plane coherence with the substrate, exhibit layer-by-layer growth and have well-defined thickness fringes in x-ray diffraction measurements. Atomic force microscopy (AFM) measurements indicate that misfit dislocations form in thicker films and the critical thickness for the dislocation formation is estimated. Perpendicular magnetic anisotropy in CFO due to epitaxial in-plane tensile strain from the substrate was found. A stripe-like domain structure in the demagnetized state is demonstrated using magnetic force microscopy (MFM), in agreement with previous predictions. Coercivity increased in thicker films, which is explained by domain wall pinning due to misfit dislocations at the CFO/MgO interface. - Highlights: → X-ray diffraction and rocking curves indicate films are amongst highest quality in the literature. → Domain structure of CoFe 2 O 4 films on MgO was found to be stripe-like using MFM. → Critical thickness for misfit dislocations estimated and agrees with experiment. → Effect of misfit dislocations on surface morphology explained. → Role of dislocations and antiphase boundaries in domain wall formation and motion explained.

  17. Current induced domain wall motion and tilting in Pt/Co/Ta structures with perpendicular magnetic anisotropy in the presence of the Dyzaloshinskii–Moriya interaction

    Science.gov (United States)

    Yun, Jijun; Li, Dong; Cui, Baoshan; Guo, Xiaobin; Wu, Kai; Zhang, Xu; Wang, Yupei; Mao, Jian; Zuo, Yalu; Xi, Li

    2018-04-01

    Current induced domain wall motion (CIDWM) was studied in Pt/Co/Ta structures with perpendicular magnetic anisotropy and the Dyzaloshinskii–Moriya interaction (DMI) by the spin-orbit torque (SOT). We measured the strength of DMI and SOT efficiency in Pt/Co/Ta with the variation of the thickness of Ta using a current induced hysteresis loop shift method. The results indicate that the DMI stabilizes a chiral Néel-type domain wall (DW), and the DW motion can be driven by the enhanced large SOT generated from Pt and Ta with opposite signs of spin Hall angle in Pt/Co/Ta stacks. The CIDWM velocity, which is 104 times larger than the field driven DW velocity, obeys a creep law, and reaches around tens of meters per second with current density of ~106 A cm‑2. We also found that the Joule heating accompanied with current also accelerates the DW motion. Meanwhile, a domain wall tilting was observed, which increases with current density increasing. These results can be explained by the spin Hall effect generated from both heavy metals Pt and Ta, inherent DMI, and the current accompanying Joule heating effect. Our results could provide some new designing prospects to move multiple DWs by SOT for achieving racetrack memories.

  18. Fast switching and signature of efficient domain wall motion driven by spin-orbit torques in a perpendicular anisotropy magnetic insulator/Pt bilayer

    Science.gov (United States)

    Avci, Can Onur; Rosenberg, Ethan; Baumgartner, Manuel; Beran, Lukáš; Quindeau, Andy; Gambardella, Pietro; Ross, Caroline A.; Beach, Geoffrey S. D.

    2017-08-01

    We report fast and efficient current-induced switching of a perpendicular anisotropy magnetic insulator thulium iron garnet by using spin-orbit torques (SOT) from the Pt overlayer. We first show that, with quasi-DC (10 ms) current pulses, SOT-induced switching can be achieved with an external field as low as 2 Oe, making TmIG an outstanding candidate to realize efficient switching in heterostructures that produce moderate stray fields without requiring an external field. We then demonstrate deterministic switching with fast current pulses (≤20 ns) with an amplitude of ˜1012 A/m2, similar to all-metallic structures. We reveal that, in the presence of an initially nucleated domain, the critical switching current is reduced by up to a factor of five with respect to the fully saturated initial state, implying efficient current-driven domain wall motion in this system. Based on measurements with 2 ns-long pulses, we estimate the domain wall velocity of the order of ˜400 m/s per j = 1012 A/m2.

  19. Model of inter-cell interference phenomenon in 10 nm magnetic tunnel junction with perpendicular anisotropy array due to oscillatory stray field from neighboring cells

    Science.gov (United States)

    Ohuchida, Satoshi; Endoh, Tetsuo

    2018-06-01

    In this paper, we propose a new model of inter-cell interference phenomenon in a 10 nm magnetic tunnel junction with perpendicular anisotropy (p-MTJ) array and investigated the interference effect between a program cell and unselected cells due to the oscillatory stray field from neighboring cells by Landau–Lifshitz–Gilbert micromagnetic simulation. We found that interference brings about a switching delay in a program cell and excitation of magnetization precession in unselected cells even when no programing current passes through. The origin of interference is ferromagnetic resonance between neighboring cells. During the interference period, the precession frequency of the program cell is 20.8 GHz, which synchronizes with that of the theoretical precession frequency f = γH eff in unselected cells. The disturbance strength of unselected cells decreased to be inversely proportional to the cube of the distance from the program cell, which is in good agreement with the dependence of stray field on the distance from the program cell calculated by the dipole approximation method.

  20. Highly (001) oriented L1{sub 0}-CoPt/TiN multilayer films on glass substrates with perpendicular magnetic anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    An, Hongyu; Sannomiya, Takumi; Muraishi, Shinji; Nakamura, Yoshio; Shi, Ji, E-mail: shi.j.aa@m.titech.ac.jp [Department of Metallurgy and Ceramics Science, Tokyo Institute of Technology, 2-12-1, Ookayama, Meguro-ku, Tokyo 152-8552 (Japan); Xie, Qian; Zhang, Zhengjun [Key Laboratory of Advanced Materials, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Wang, Jian [National Institute for Materials Science (NIMS), Sengen 1-2-1, Tsukuba, Ibaraki 305-0047 (Japan)

    2015-03-15

    To obtain strong perpendicular magnetic anisotropy (PMA) based on L1{sub 0} structure for magnetic storage devices, costly single crystalline substrates are generally required to achieve (001) texture. Recently, various studies also have focused on depositing different kinds of seed layers on glass or other amorphous substrates to promote (001) preferred orientation of L1{sub 0} CoPt and FePt. TiN is a very promising seed layer material because of its cubic crystalline structure (similar to MgO) and excellent diffusion barring property even at high temperatures. In the present work, highly (001) oriented L1{sub 0}-CoPt/TiN multilayer films have been successfully deposited on glass substrates. After annealing at 700 °C, the film exhibits PMA, and a strong (001) peak is detected from the x-ray diffraction profiles, indicating the ordering transformation of CoPt layers from fcc (A1) to L1{sub 0} structure. It also is found that alternate deposition of cubic TiN and CoPt effectively improves the crystallinity and (001) preferred orientation of CoPt layers. This effect is verified by the substantial enhancement of (001) reflection and PMA with increasing the period number of the multilayer films.

  1. Time scales of bias voltage effects in FE/MgO-based magnetic tunnel junctions with voltage-dependent perpendicular anisotropy

    International Nuclear Information System (INIS)

    Lytvynenko, Ia.M.; Hauet, T.; Montaigne, F.; Bibyk, V.V.; Andrieu, S.

    2015-01-01

    Interplay between voltage-induced magnetic anisotropy transition and voltage-induced atomic diffusion is studied in epitaxial V/Fe (0.7 nm)/ MgO/ Fe(5 nm)/Co/Au magnetic tunnel junction where thin Fe soft electrode has in-plane or out-of-plane anisotropy depending on the sign of the bias voltage. We investigate the origin of the slow resistance variation occurring when switching bias voltage in opposite polarity. We demonstrate that the time to reach resistance stability after voltage switching is reduced when increasing the voltage amplitude or the temperature. A single energy barrier of about 0.2 eV height is deduced from temperature dependence. Finally, we demonstrate that the resistance change is not correlated to a change in soft electrode anisotropy. This conclusion contrasts with observations recently reported on analogous systems. - Highlights: • Voltage-induced time dependence of resistance is studied in epitaxial Fe/MgO/Fe. • Resistance change is not related to the bottom Fe/MgO interface. • The effect is thermally activated with an energy barrier of the order of 0.2 eV height

  2. Giant Spin Hall Effect and Switching Induced by Spin-Transfer Torque in a W /Co40Fe40B20/MgO Structure with Perpendicular Magnetic Anisotropy

    Science.gov (United States)

    Hao, Qiang; Xiao, Gang

    2015-03-01

    We obtain robust perpendicular magnetic anisotropy in a β -W /Co40Fe40B20/MgO structure without the need of any insertion layer between W and Co40Fe40B20 . This is achieved within a broad range of W thicknesses (3.0-9.0 nm), using a simple fabrication technique. We determine the spin Hall angle (0.40) and spin-diffusion length for the bulk β form of tungsten with a large spin-orbit coupling. As a result of the giant spin Hall effect in β -W and careful magnetic annealing, we significantly reduce the critical current density for the spin-transfer-torque-induced magnetic switching in Co40Fe40B20 . The elemental β -W is a superior candidate for magnetic memory and spin-logic applications.

  3. Origin of variation of shift field via annealing at 400°C in a perpendicular-anisotropy magnetic tunnel junction with [Co/Pt]-multilayers based synthetic ferrimagnetic reference layer

    Directory of Open Access Journals (Sweden)

    H. Honjo

    2017-05-01

    Full Text Available We investigated properties of perpendicular-anisotropy magnetic tunnel junctions (p-MTJs with [Co/Pt]-multilayer based synthetic ferrimagnetic reference (SyF layer at elevated annealing temperature Ta from 350°C to 400°C. Shift field HS defined as center field of minor resistance versus magnetic field curve of the MTJs increased with increase of Ta from 350°C to 400°C. The variation of HS is attributed to the variation of saturation magnetic moment in the SyF reference layer. Cross sectional energy dispersive X-ray spectroscopy analysis revealed that Fe element of CoFeB in the reference layer diffuses to Co/Pt multilayers in the SyF reference layer.

  4. Ferromagnetic resonance frequency increase and resonance line broadening of a ferromagnetic Fe–Co–Hf–N film with in-plane uniaxial anisotropy by high-frequency field perturbation

    International Nuclear Information System (INIS)

    Seemann, K.; Leiste, H.; Krüger, K.

    2013-01-01

    Soft ferromagnetic Fe-Co-Hf-N films, produced by reactive r.f. magnetron sputtering, are useful to study the ferromagnetic resonance (FMR) by means of frequency domain permeability measurements up to the GHz range. Films with the composition Fe 33 Co 43 Hf 10 N 14 exhibit a saturation polarisation J s of around 1.35 T. They are consequently considered as being uniformly magnetised due to an in-plane uniaxial anisotropy of approximately μ 0 H u ≈4.5 m T after annealing them, e.g., at 400 °C in a static magnetic field for 1 h. Being exposed to a high-frequency field, the precession of magnetic moments leads to a marked frequency-dependent permeability with a sharp Lorentzian shaped imaginary part at around 2.33 GHz (natural resonance peak), which is in a very good agreement with the modified Landau–Lifschitz–Gilbert (LLG) differential equation. A slightly increased FMR frequency and a clear increase in the resonance line broadening due to an increase of the exciting high-frequency power (1–25.1 mW), considered as an additional perturbation of the precessing system of magnetic moments, could be discovered. By solving the homogenous LLG differential equation with respect to the in-plane uniaxial anisotropy, it was revealed that the high-frequency field perturbation impacts the resonance peak position f FMR and resonance line broadening Δf FMR characterised by a completed damping parameter α=α eff +Δα. Adapted from this result, the increase in f FMR and decrease in lifetime of the excited level of magnetic moments associated with Δf FMR , similar to a spin-½ particle in a static magnetic field, was theoretically elaborated as well as compared with experimental data. - Highlights: • Impact on the resonance frequency and resonance line by the high-frequency power. • Theoretic approach by solving the LLG differential equation. • Experimental verification and magnon processes. • Theoretical and experimental determination of the resonance state

  5. Perpendicular magnetic anisotropy in Mo/Co2FeAl0.5Si0.5/MgO/Mo multilayers with optimal Mo buffer layer thickness

    Science.gov (United States)

    Saravanan, L.; Raja, M. Manivel; Prabhu, D.; Pandiyarasan, V.; Ikeda, H.; Therese, H. A.

    2018-05-01

    Perpendicular Magnetic Anisotropy (PMA) was realized in as-deposited Mo(10)/Co2FeAl0.5Si0.5(CFAS)(3)/MgO(0.5)/Mo multilayer stacks with large perpendicular magnetic anisotropy energy (Keff). PMA of this multilayer is found to be strongly dependent on the thickness of the individual CFAS (tCFAS), Mo (tMo) and MgO (tMgO) layers and annealing temperatures. The interactions at the Mo/CFAS/MgO interfaces are critical to induce PMA and are tuned by the interfacial oxidation. The major contribution to PMA is due to iron oxide at the CFAS/MgO interface. X-ray diffraction (XRD) and infrared spectroscopic (FT-IR) studies further ascertain this. However, an adequate oxidation of MgO and the formation of (0 2 4) and (0 1 8) planes of α-Fe2O3 at the optimal Mo buffer layer thickness is mainly inducing PMA in Mo/CFAS/MgO/Mo stack. Microstructural changes in the films are observed by atomic force microscopy (AFM). X-ray photoelectron spectroscopy (XPS) demonstrates the oxidation of CFAS/MgO interface and the formation of Fe-O bonds confirming that the real origin of PMA in Mo/CFAS/MgO is due to hybridization of Fe (3dz2) and O (2pz) orbitals and the resulted spin-orbit interaction at their interface. The half-metallic nature CFAS with Mo layer exhibiting PMA can be a potential candidate as p-MTJs electrodes for the new generation spintronic devices.

  6. Electric anisotropy in high density polyethylene + carbon black composites induced by mechanical deformation

    Energy Technology Data Exchange (ETDEWEB)

    Vigueras-Santiago, E; Hernandez-Lopez, S; Camacho-Lopez, M A; Lara-Sanjuan, O, E-mail: eviguerass@uaemex.m [Laboratorio de Investigacion y Desarrollo de Materiales Avanzados (LIDMA), Facultad de Quimica, UAEM. Paseo Colon esq. con Paseo Tollocan, s/n. C.P. 50000, Toluca (Mexico)

    2009-05-01

    High density polyethylene + carbon black composites with electrical anisotropy was studied. Electrical anisotropy was induced by uniaxial mechanical deformation and injection moulding. We show that anisotropy depends on the carbon black concentration and percentage deformation. Resistivity had the highest anisotropy resistivity around the percolation threshold. Perpendicular resistivity showed two magnitude orders higher than parallel resistivity for injected samples, whereas resistivity showed an inverse behaviour for 100% tensile samples. Both directions were set respect to the deformation axe. Anisotropy could be explained in terms of the molecular deformation (alignment) of the polymer chains as a response of the deformation process originating a redistribution of the carbon black particles in both directions. Alignment of the polymer chains was evidenced by polarized Raman spectroscopy.

  7. Magnetic anisotropies in ultrathin bismuth iron garnet films

    International Nuclear Information System (INIS)

    Popova, Elena; Franco Galeano, Andres Felipe; Deb, Marwan; Warot-Fonrose, Bénédicte; Kachkachi, Hamid; Gendron, François; Ott, Frédéric

    2013-01-01

    Ultrathin bismuth iron garnet Bi 3 Fe 5 O 12 films were grown epitaxially on (001)-oriented gadolinium gallium garnet substrates. Film thickness varied from two to three dozens of unit cells. Bi 3 Fe 5 O 12 films grow pseudomorphically on substrates up to a thickness of 20 nm, and then a lattice relaxation occurs. Magnetic properties of the films were studied as a function of bismuth iron garnet thickness. The magnetization and cubic anisotropy decrease with decreasing film thickness. The uniaxial magnetocrystalline anisotropy is constant for all film thicknesses. For two unit cell thick films, the easy magnetization axis changes from in-plane to perpendicular to the plane direction. Such a reorientation takes place as a result of the competition of constant uniaxial perpendicular anisotropy with weakening film magnetization. - Highlights: ► Ultrathin Bi 3 Fe 5 O 12 films were grown epitaxially on structure-matching substrates. ► Magnetic properties of Bi 3 Fe 5 O 12 were studied down to the thickness of 2.5 nm. ► Reorientation of easy magnetization axis as a function of film thickness was observed

  8. Magnetic anisotropies in ultrathin bismuth iron garnet films

    Energy Technology Data Exchange (ETDEWEB)

    Popova, Elena, E-mail: popova@physique.uvsq.fr [Groupe d' Etude de la Matière Condensée (GEMaC), CNRS/Université de Versailles-Saint-Quentin, 45 Avenue des Etats-Unis, 78035 Versailles (France); Franco Galeano, Andres Felipe [Laboratoire PROcédés, Matériaux et Energie Solaire (PROMES), CNRS/Université de Perpignan Via Domitia, 52 Avenue Paul Alduy, 66860 Perpignan (France); Deb, Marwan [Groupe d' Etude de la Matière Condensée (GEMaC), CNRS/Université de Versailles-Saint-Quentin, 45 Avenue des Etats-Unis, 78035 Versailles (France); Warot-Fonrose, Bénédicte [Centre d' Elaboration de Matériaux et d' Etudes Structurales (CEMES), CNRS, 29 rue Jeanne Marvig, 31055 Toulouse (France); Transpyrenean Associated Laboratory for Electron Microscopy (TALEM), CEMES-INA, CNRS–Universidad de Zaragoza (Spain); Kachkachi, Hamid [Laboratoire PROcédés, Matériaux et Energie Solaire (PROMES), CNRS/Université de Perpignan Via Domitia, 52 Avenue Paul Alduy, 66860 Perpignan (France); Gendron, François [Institut des NanoSciences de Paris (INSP), CNRS/Université Pierre et Marie Curie-Paris 6, 4 place Jussieu, Boîte courrier 840, 75252 Paris Cedex 05 (France); Ott, Frédéric [Laboratoire Léon Brillouin (LLB), CNRS/CEA, Bâtiment 563, CEA Saclay, 91191 Gif sur Yvette Cedex (France); and others

    2013-06-15

    Ultrathin bismuth iron garnet Bi{sub 3}Fe{sub 5}O{sub 12} films were grown epitaxially on (001)-oriented gadolinium gallium garnet substrates. Film thickness varied from two to three dozens of unit cells. Bi{sub 3}Fe{sub 5}O{sub 12} films grow pseudomorphically on substrates up to a thickness of 20 nm, and then a lattice relaxation occurs. Magnetic properties of the films were studied as a function of bismuth iron garnet thickness. The magnetization and cubic anisotropy decrease with decreasing film thickness. The uniaxial magnetocrystalline anisotropy is constant for all film thicknesses. For two unit cell thick films, the easy magnetization axis changes from in-plane to perpendicular to the plane direction. Such a reorientation takes place as a result of the competition of constant uniaxial perpendicular anisotropy with weakening film magnetization. - Highlights: ► Ultrathin Bi{sub 3}Fe{sub 5}O{sub 12} films were grown epitaxially on structure-matching substrates. ► Magnetic properties of Bi{sub 3}Fe{sub 5}O{sub 12} were studied down to the thickness of 2.5 nm. ► Reorientation of easy magnetization axis as a function of film thickness was observed.

  9. High-resolution vector magnetometry: Piezo-spin-polarization effect and in-plane strain-induced dominating uniaxial magnetic anisotropy in a 200-nm-thick Ni thin film

    Science.gov (United States)

    Benito, L.

    2018-04-01

    Owing to its high-sensitivity, reliability, fast, versatile and cost-effective operation, vibrating sample magnetometers (VSM) are massively popular characterization instruments at Magnetism laboratories worldwide. Nevertheless, the inherent appearance of synchronous noise represents a major drawback, which critically limits the fine probing of nanometer-sized media. I here report on an innovative approach to eliminate synchronous noise in VSM. This consists of fitting engineered mechanical devices that absorbs vibration energy, dissipating that into heat. Complementarily, a novel transversal pick-up coil system is also presented and analyzed; this detection system has been engineered to enhance the noise-to-signal ratio and optimized for measuring small size thin film samples. The implementation of a combined mechanical and electromagnetic approach enables to notably enhance the VSM performance, achieving a sensitivity better than 1 ×10-6 emu and a resolution below 5 ×10-8 emu, so that the magnetization vector in nanostructured media can be accurately mapped out down to cryogenic temperatures. I lastly show precision magnetometry measurements carried out in an epitaxial (0 0 1)-oriented 200 nm-thick Ni thin film. The analysis reveals the arising of an in-plane dominating strain-induced uniaxial magnetic anisotropy, K2ef = - 6.455kJ m - 3 , and a stunning piezo-spin-polarization effect resulting in a remarkable 10% modulation of the magnetization vector, ∼ 27 emu/cm3, with respect to the cubic lattice axes. Both effects are attributed to the likely existence of an orthorhombic lattice distortion, i.e.εxx -εyy ≈ - 2 ×10-3 . This categorical link enables to assign the observed anisotropic spin-polarization in the Ni overlayer to a two-ion magnetoelastic coupling effect.

  10. Correlation between physical structure and magnetic anisotropy of a magnetic nanoparticle colloid

    Science.gov (United States)

    Dennis, C. L.; Jackson, A. J.; Borchers, J. A.; Gruettner, C.; Ivkov, R.

    2018-05-01

    We show the effects of a time-invariant magnetic field on the physical structure and magnetic properties of a colloid comprising 44 nm diameter magnetite magnetic nanoparticles, with a 24 nm dextran shell, in water. Structural ordering in this colloid parallel to the magnetic field occurs simultaneously with the onset of a colloidal uniaxial anisotropy. Further increases in the applied magnetic field cause the nanoparticles to order perpendicular to the field, producing unexpected colloidal unidirectional and trigonal anisotropies. This magnetic behavior is distinct from the cubic magnetocrystalline anisotropy of the magnetite and has its origins in the magnetic interactions among the mobile nanoparticles within the colloid. Specifically, these field-induced anisotropies and colloidal rearrangements result from the delicate balance between the magnetostatic and steric forces between magnetic nanoparticles. These magnetic and structural rearrangements are anticipated to influence applications that rely upon time-dependent relaxation of the magnetic colloids and fluid viscosity, such as magnetic hyperthermia and shock absorption.

  11. A magneto-optic technique for studying magnetization reversal processes and anisotropies applied to Co/Cu/Co trilayer structures

    Science.gov (United States)

    Daboo, C.; Bland, J. A. C.; Hicken, R. J.; Ives, A. J. R.; Baird, M. J.; Walker, M. J.

    1993-05-01

    We report the magnetization reversal and magnetic anisotropy behavior of ultrathin Co/Cu(111)/Co (dCu=20 and 27 Å) trilayer structures prepared by MBE on a 500-Å Ge/GaAs(110) epilayer. We describe an arrangement in which the magnetization components parallel and perpendicular to the applied field are both determined from longitudinal MOKE measurements. For the samples examined, coherent rotation of the magnetization vector is observed when the magnetic field is applied along the hard in-plane anisotropy axis, with the magnitude of the magnetization vector constant and close to its bulk value. Results of micromagnetic calculations closely reproduce the observed parallel and perpendicular magnetization loops, and yield strong uniaxial magnetic anisotropies in both layers while the interlayer coupling appears to be absent or negligible in comparison with the anisotropy strengths. An absence of antiferromagnetic (AF) coupling has been observed previously [W. F. Egelhoff, Jr. and M. T. Kief, Phys. Rev. B 45, 7795 (1992)] in contrast to recent results, indicating that AF coupling [M. T. Johnson et al., Phys. Rev. Lett. 69, 969 (1992)] and GMR [D. Grieg et al., J. Magn. Magn. Mater. 110, L239 (1992)] can occur in Co/Cu(111)/Co structures grown by MBE, but these properties are sensitively dependent on growth conditions. The absence of coupling in our samples is attributed to the presence of a significant interface roughness induced by the Ge epilayer. The uniaxial anisotropies are assumed to arise from strain or defects induced in the film.

  12. Laser heating and oxygen partial pressure effects on the dynamic magnetic properties of perpendicular CoFeAlO films

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Di [Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education), Department of Optical Science and Engineering, Fudan University, Shanghai 200433 (China); Li, Wei [State Key Laboratory of Precision Spectroscopy and Department of Physics, East China Normal University, Shanghai 200062 (China); Tang, Minghong [Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education), Department of Optical Science and Engineering, Fudan University, Shanghai 200433 (China); Zhang, Zongzhi, E-mail: zzzhang@fudan.edu.cn [Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education), Department of Optical Science and Engineering, Fudan University, Shanghai 200433 (China); Lou, Shitao [State Key Laboratory of Precision Spectroscopy and Department of Physics, East China Normal University, Shanghai 200062 (China); Jin, Q.Y. [Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education), Department of Optical Science and Engineering, Fudan University, Shanghai 200433 (China); State Key Laboratory of Precision Spectroscopy and Department of Physics, East China Normal University, Shanghai 200062 (China)

    2016-07-01

    The impact of oxidation and laser heating on the dynamic magnetic properties of perpendicularly magnetized Co{sub 50}Fe{sub 25}Al{sub 25}O films has been studied by time-resolved magneto-optical Kerr effect in a fs-laser pump-probe setup. We find that pump laser fluence F{sub p} can affect the effective magnetic anisotropy field and thus the precession frequency f seriously, leading to an increased dependence of effective magnetic damping factor α{sub eff} on the external field at higher fluences. Moreover, the α{sub eff} increases with increasing the oxygen partial pressure P{sub O2} while the uniaxial anisotropy energy K{sub u} and Landau factor g decrease, owing to the increased proportion of superparamagnetic CoFe oxides formed by over-oxidation. By optimizing both the F{sub p} and P{sub O2}, the intrinsic damping factor is determined to be lower than 0.028 for the perpendicular film showing a uniaxial anisotropy energy as high as 4.3×10{sup 6} erg/cm{sup 3}. The results in this study provide a promising approach to manipulate the magnetic parameters for possible applications in spintronic devices. - Highlights: • A new kind of perpendicular thin film material, oxidized CoFeAl, has been fabricated. • The precession frequency and effective damping are strongly affected by higher fluence. • The effective damping factor increases with oxygen partial pressure. • The intrinsic damping factor is below 0.028 for the CFAO film with K{sub u}=4.3×10{sup 6} erg/cm{sup 3}.

  13. Layering and temperature-dependent magnetization and anisotropy of naturally produced Ni/NiO multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Pappas, S. D.; Trachylis, D.; Velgakis, M. J. [Laboratory of High-Tech Materials, School of Engineering, University of Patras, 26504 Patras (Greece); Kapaklis, V.; Joensson, P. E.; Papaioannou, E. Th. [Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala (Sweden); Delimitis, A. [Chemical Process Engineering Research Institute (CPERI), Centre for Research and Technology Hellas (CERTH), 57001 Thermi, Thessaloniki (Greece); Poulopoulos, P. [Laboratory of High-Tech Materials, School of Engineering, University of Patras, 26504 Patras (Greece); Institut fuer Experimentalphysik, Freie Universitaet Berlin, Arnimallee 14, D-14195 Berlin-Dahlem (Germany); Materials Science Department, University of Patras, 26504 Patras (Greece); Fumagalli, P. [Institut fuer Experimentalphysik, Freie Universitaet Berlin, Arnimallee 14, D-14195 Berlin-Dahlem (Germany); Politis, C. [Laboratory of High-Tech Materials, School of Engineering, University of Patras, 26504 Patras (Greece); Department of Materials Science and Engineering, University of Texas at Arlington, Arlington, Texas 76019 (United States)

    2012-09-01

    Ni/NiO multilayers were grown by magnetron sputtering at room temperature, with the aid of the natural oxidation procedure. That is, at the end of the deposition of each single Ni layer, air is let to flow into the vacuum chamber through a leak valve. Then, a very thin NiO layer ({approx}1.2 nm) is formed. Simulated x-ray reflectivity patterns reveal that layering is excellent for individual Ni-layer thickness larger than 2.5 nm, which is attributed to the intercalation of amorphous NiO between the polycrystalline Ni layers. The magnetization of the films, measured at temperatures 5-300 K, has almost bulk-like value, whereas the films exhibit a trend to perpendicular magnetic anisotropy (PMA) with an unusual significant positive interface anisotropy contribution, which presents a weak temperature dependence. The power-law behavior of the multilayers indicates a non-negligible contribution of higher order anisotropies in the uniaxial anisotropy. Bloch-law fittings for the temperature dependence of the magnetization in the spin-wave regime show that the magnetization in the multilayers decreases faster as a function of temperature than the one of bulk Ni. Finally, when the individual Ni-layer thickness decreases below 2 nm, the multilayer stacking vanishes, resulting in a dramatic decrease of the interface magnetic anisotropy and consequently in a decrease of the perpendicular magnetic anisotropy.

  14. Magnetic anisotropy, damping, and interfacial spin transport in Pt/LSMO bilayers

    Directory of Open Access Journals (Sweden)

    H. K. Lee

    2016-05-01

    Full Text Available We report ferromagnetic resonance measurements of magnetic anisotropy and damping in epitaxial La0.7Sr0.3MnO3 (LSMO and Pt capped LSMO thin films on SrTiO3 (001 substrates. The measurements reveal large negative perpendicular magnetic anisotropy and a weaker uniaxial in-plane anisotropy that are unaffected by the Pt cap. The Gilbert damping of the bare LSMO films is found to be low α = 1.9(1 × 10−3, and two-magnon scattering is determined to be significant and strongly anisotropic. The Pt cap increases the damping by 50% due to spin pumping, which is also directly detected via inverse spin Hall effect in Pt. Our work demonstrates efficient spin transport across the Pt/LSMO interface.

  15. Magnetic anisotropy, damping, and interfacial spin transport in Pt/LSMO bilayers

    Energy Technology Data Exchange (ETDEWEB)

    Lee, H. K., E-mail: hankl@uci.edu; Barsukov, I.; Yang, L.; Krivorotov, I. N. [Physics and Astronomy, University of California, Irvine, California 92697 (United States); Swartz, A. G.; Kim, B. [Geballe Laboratory for Advanced Materials, Department of Applied Physics, Stanford University, Stanford, California 94305 (United States); Hwang, H. Y. [Geballe Laboratory for Advanced Materials, Department of Applied Physics, Stanford University, Stanford, California 94305 (United States); Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States)

    2016-05-15

    We report ferromagnetic resonance measurements of magnetic anisotropy and damping in epitaxial La{sub 0.7}Sr{sub 0.3}MnO{sub 3} (LSMO) and Pt capped LSMO thin films on SrTiO{sub 3} (001) substrates. The measurements reveal large negative perpendicular magnetic anisotropy and a weaker uniaxial in-plane anisotropy that are unaffected by the Pt cap. The Gilbert damping of the bare LSMO films is found to be low α = 1.9(1) × 10{sup −3}, and two-magnon scattering is determined to be significant and strongly anisotropic. The Pt cap increases the damping by 50% due to spin pumping, which is also directly detected via inverse spin Hall effect in Pt. Our work demonstrates efficient spin transport across the Pt/LSMO interface.

  16. Uniaxial in-plane magnetization of iron nanolayers grown within an amorphous matrix

    Energy Technology Data Exchange (ETDEWEB)

    Ghafari, M., E-mail: mohammad.ghafari@kit.edu; Hahn, H. [Herbert Gleiter Institute of Nanoscience, Nanjing University of Science and Technology, Nanjing 210094 (China); Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); Mattheis, R. [Leibniz Institute for Photonic Technology IPHT, Jena (Germany); McCord, J. [Institute for Materials Science, Kiel University Kiel, Kaiserstraße 2, 24143 Kiel (Germany); Brand, R. A. [Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); Macedo, W. A. A. [Laboratório de Física Aplicada, Centro de Desenvolvimento da Tecnologia Nuclear (CDTN), 31270-901 Belo Horizonte, MG (Brazil)

    2014-08-18

    Conversion electron Mössbauer spectroscopy is used to determine the magnetic ground state at zero magnetic field of four-monolayer thick amorphous iron layers as part of a CoFeB-Fe multilayer stack. By comparing the intensities of the magnetic hyperfine field, an easy in-plane axis of the amorphous embedded Fe layer is verified, which is collinear to the uniaxial anisotropy axis of the neighboring amorphous CoFeB. Despite the soft magnetic character of the Fe layers, external fields up to 4 T perpendicular to the film plane are insufficient to completely align the embedded Fe moments parallel to the magnetic field due to a local disorder of the magnetic moments of the Fe atoms.

  17. Fourfold magnetic anisotropy, coercivity and magnetization reversal of Co/V bilayers grown on MgO(0 0 1)

    International Nuclear Information System (INIS)

    Calleja, J F; Muro, M GarcIa del; Presa, B; Matarranz, R; Corrales, J A; Labarta, A; Contreras, M C

    2007-01-01

    Magnetic anisotropy and magnetization reversal of Al/Co/V/MgO(0 0 1) thin films have been investigated. The films were fabricated by magnetron sputtering. The roles of both Co and V layers thicknesses have been studied. Magnetic characterization has been carried out by transverse susceptibility (TS) measurements and hysteresis loops. Cobalt is grown in the hcp structure on V with the c axis parallel to the film plane. Two types of hcp Co crystal are grown with the c axes perpendicular to each other. This structure gives rise to a fourfold magnetic anisotropy. When the V layer thickness is below 40 A a superimposed uniaxial anisotropy develops, the effect of which is a depression in the TS, in agreement with theoretical calculations. This uniaxial anisotropy is induced by the substrate and due to a discontinuous growth of the V layer. For hcp Co grown on V, the magnetic anisotropy rapidly increases with Co layer thickness. In this case, unexpected shifted hysteresis loops along the hard axes were observed when the films were not saturated. This has been explained by taking into account the magnetization reversal along the hard axis: it proceeds via magnetization rotation of some portions of the film at high fields, and by domain wall motion of the rest of the film at lower field values

  18. Fourfold magnetic anisotropy, coercivity and magnetization reversal of Co/V bilayers grown on MgO(0 0 1)

    Energy Technology Data Exchange (ETDEWEB)

    Calleja, J F [Departamento de Fisica, Facultad de Ciencias, Universidad de Oviedo, Calvo Sotelo s/n, 33007 Oviedo (Spain); Muro, M GarcIa del [Departament de Fisica Fonamental and Institut de Nanociencia i Nanotecnologia IN2UB de la Universitat de Barcelona, MartIi Franques, 1, E-08028 Barcelona (Spain); Presa, B [Departamento de Fisica, Facultad de Ciencias, Universidad de Oviedo, Calvo Sotelo s/n, 33007 Oviedo (Spain); Matarranz, R [Departamento de Fisica, Facultad de Ciencias, Universidad de Oviedo, Calvo Sotelo s/n, 33007 Oviedo (Spain); Corrales, J A [Departmento de Informatica, Universidad de Oviedo, Edificio Departamental 1, Campus de Viesques s/n, 33204 Gijon (Spain); Labarta, A [Departament de Fisica Fonamental and Institut de Nanociencia i Nanotecnologia IN2UB de la Universitat de Barcelona, MartIi Franques, 1, E-08028 Barcelona (Spain); Contreras, M C [Departamento de Fisica, Facultad de Ciencias, Universidad de Oviedo, Calvo Sotelo s/n, 33007 Oviedo (Spain)

    2007-11-21

    Magnetic anisotropy and magnetization reversal of Al/Co/V/MgO(0 0 1) thin films have been investigated. The films were fabricated by magnetron sputtering. The roles of both Co and V layers thicknesses have been studied. Magnetic characterization has been carried out by transverse susceptibility (TS) measurements and hysteresis loops. Cobalt is grown in the hcp structure on V with the c axis parallel to the film plane. Two types of hcp Co crystal are grown with the c axes perpendicular to each other. This structure gives rise to a fourfold magnetic anisotropy. When the V layer thickness is below 40 A a superimposed uniaxial anisotropy develops, the effect of which is a depression in the TS, in agreement with theoretical calculations. This uniaxial anisotropy is induced by the substrate and due to a discontinuous growth of the V layer. For hcp Co grown on V, the magnetic anisotropy rapidly increases with Co layer thickness. In this case, unexpected shifted hysteresis loops along the hard axes were observed when the films were not saturated. This has been explained by taking into account the magnetization reversal along the hard axis: it proceeds via magnetization rotation of some portions of the film at high fields, and by domain wall motion of the rest of the film at lower field values.

  19. In situ synchrotron X-ray diffraction of ferroelastic La0.8Ca0.2CoO3 ceramics during uniaxial compression

    International Nuclear Information System (INIS)

    Vullum, Per Erik; Mastin, Johann; Wright, Jonathan; Einarsrud, Mari-Ann; Holmestad, Randi; Grande, Tor

    2006-01-01

    Uniaxial compression of rhombohedral La 0.8 Ca 0.2 CoO 3 ceramics has been studied in situ using synchrotron X-ray diffraction. The intensities of Bragg reflections parallel and perpendicular to the stress field were simultaneously detected as a function of the stress. Reorientation of ferroelastic domains due to the uniaxial stress was demonstrated. With increasing stress the volume fraction of domains with the hexagonal c-axis parallel to the stress axis increased at the expense of domains with the c-axis perpendicular to the stress axis. The strain in the polycrystalline materials evolved unevenly with increasing stress due to crystallographic anisotropy. In energetically favourable domains with the c-axis parallel to the stress axis, the rhombohedral distortion from cubic symmetry increased, while the crystal structure became closer to cubic in domains with the c-axis perpendicular to the stress. Successive compression/decompression cycles to higher maximum stress resulted in a higher volume fraction of reoriented domains both at maximum stress and after decompression

  20. State diagram of a perpendicular magnetic tunnel junction driven by spin transfer torque: A power dissipation approach

    Energy Technology Data Exchange (ETDEWEB)

    Lavanant, M. [Institut Jean Lamour, UMR CNRS 7198 – Université de Lorraine, Nancy (France); Department of Physics, New York University, New York, NY 10003 (United States); Petit-Watelot, S. [Institut Jean Lamour, UMR CNRS 7198 – Université de Lorraine, Nancy (France); Kent, A.D. [Department of Physics, New York University, New York, NY 10003 (United States); Mangin, S., E-mail: stephane.mangin@univ-lorraine.fr [Institut Jean Lamour, UMR CNRS 7198 – Université de Lorraine, Nancy (France)

    2017-04-15

    The state diagram of a magnetic tunnel junction with perpendicularly magnetized electrodes in the presence of spin-transfer torques is computed in a macrospin approximation using a power dissipation model. Starting from the macrospin's energy we determine the stability of energy extremum in terms of power received and dissipated, allowing the consideration of non-conservative torques associated with spin transfer and damping. The results are shown to be in agreement with those obtained by direct integration of the Landau-Lifshitz-Gilbert-Slonczewski equation. However, the power dissipation model approach is faster and shows the reason certain magnetic states are stable, such as states that are energy maxima but are stabilized by spin transfer torque. Breaking the axial system, such as by a tilted applied field or tilted anisotropy, is shown to dramatically affect the state diagrams. Finally, the influence of a higher order uniaxial anisotropy that can stabilize a canted magnetization state is considered and the results are compared to experimental data. - Highlights: • Methods to compute state Diagram (Voltage Versus Field) for perpendicular Magnetic Tunnel Junctions. • Comparison between the conventional LLG model and a model based on Power dissipation to study magnetization reversal in magnetic tunnel junction.

  1. Uniaxial backfill block compaction

    International Nuclear Information System (INIS)

    Koskinen, V.

    2012-05-01

    The main parts of the project were: to make a literature survey of the previous uniaxial compaction experiments; do uniaxial compaction tests in laboratory scale; and do industrial scale production tests. Object of the project was to sort out the different factors affecting the quality assurance chain of the backfill block uniaxial production and solve a material sticking to mould problem which appeared during manufacturing the blocks of bentonite and cruched rock mixture. The effect of mineralogical and chemical composition on the long term functionality of the backfill was excluded from the project. However, the used smectite-rich clays have been tested for mineralogical consistency. These tests were done in B and Tech OY according their SOPs. The objective of the Laboratory scale tests was to find right material- and compaction parameters for the industrial scale tests. Direct comparison between the laboratory scale tests and industrial scale tests is not possible because the mould geometry and compaction speed has a big influence for the compaction process. For this reason the selected material parameters were also affected by the previous compaction experiments. The industrial scale tests were done in summer of 2010 in southern Sweden. Blocks were done with uniaxial compaction. A 40 tons of the mixture of bentonite and crushed rock blocks and almost 50 tons of Friedland-clay blocks were compacted. (orig.)

  2. Flow stress anisotropy in aluminium

    DEFF Research Database (Denmark)

    Juul Jensen, D.; Hansen, N.

    1990-01-01

    The plastic anisotropy of cold-rolled high purity aluminum (99.996%) and commercially pure aluminum (99.6%) has been investigated. Sample parameters were the initial grain size and the degree of plastic strain (ϵ < 3.00). Flow stresses (0.2% offset) were measured at room temperature by uniaxial t...

  3. Characterization of a 14Cr ODS steel by means of small punch and uniaxial testing with regard to creep and fatigue at elevated temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Bruchhausen, M., E-mail: matthias.bruchhausen@ec.europa.eu [European Commission, Joint Research Centre, Institute for Energy and Transport, P.O. Box 2, 1755 ZG Petten (Netherlands); Turba, K. [European Commission, Joint Research Centre, Institute for Energy and Transport, P.O. Box 2, 1755 ZG Petten (Netherlands); Lund University, Division of Materials Engineering, P.O. Box 118, SE-221 00 Lund (Sweden); Haan, F. de; Hähner, P.; Austin, T. [European Commission, Joint Research Centre, Institute for Energy and Transport, P.O. Box 2, 1755 ZG Petten (Netherlands); Carlan, Y. de [CEA, DEN, Service de Recherches Métallurgiques Appliquées, 91191 Gif-sur-Yvette (France)

    2014-01-15

    A 14Cr ODS steel was characterized at elevated temperatures with regard to its behavior in small punch and uniaxial creep tests and in low cycle fatigue tests. A comparison of small punch and uniaxial creep tests at 650 °C revealed a strong anisotropy of the material when strained parallel and perpendicular to the extrusion direction with rupture times being several orders of magnitude lower for the perpendicular direction. The stress-rupture and Larson–Miller plots show a very large scatter of the creep data. This scatter is strongly reduced when rupture time is plotted against minimum deflection rate or minimum creep rate (Monkman–Grant plot). Fatigue tests have been carried out at 650 °C and 750 °C. The alloy is cyclically very stable with practically no hardening/softening. Results from the tests at both temperatures can be described by a common power law. An increase in the test temperature has little influence on the fatigue ductility exponent. For a given total strain level, the fatigue life of the alloy is reduced with increasing temperature.

  4. Ising versus XY anisotropy in frustrated R(2)Ti(2)O(7) compounds as "Seen" by Polarized Neutrons.

    Science.gov (United States)

    Cao, H; Gukasov, A; Mirebeau, I; Bonville, P; Decorse, C; Dhalenne, G

    2009-07-31

    We studied the field induced magnetic order in R(2)Ti(2)O(7) pyrochlore compounds with either uniaxial (R=Ho, Tb) or planar (R=Er, Yb) anisotropy, by polarized neutron diffraction. The determination of the local susceptibility tensor {chi(parallel to),chi(perpendicular)} provides a universal description of the field induced structures in the paramagnetic phase (2-270 K), whatever the field value (1-7 T) and direction. Comparison of the thermal variations of chi(parallel to) and chi(perpendicular) with calculations using the rare earth crystal field shows that exchange and dipolar interactions must be taken into account. We determine the molecular field tensor in each case and show that it can be strongly anisotropic.

  5. Wave and particle evolution downstream of quasi-perpendicular shocks

    Science.gov (United States)

    Mckean, M. E.; Omidi, N.; Krauss-Varban, D.; Karimabadi, H.

    1995-01-01

    Distributions of ions heated in quasi-perpendicular bow shocks have large perpendicular temperature anisotropies that provide free energy for the growth of Alfven ion cyclotron (AIC) and mirror waves. These modes are often obsreved in the Earth's magnetosheath. Using two-dimensional hybrid simulations, we show that these waves are produced near the shock front and convected downstream rather than being produced locally downstream. The wave activity reduces the proton anisotropy to magnetosheath levels within a few tens of gyroradii of the shock but takes significantly longer to reduce the anisotropy of He(++) ions. The waves are primarily driven by proton anisotropy and the dynamics of the helium ions is controlled by the proton waves. Downstream of high Mach number shocks, mirror waves compete effectively with AIC waves. Downstream of low Mach number shocks, AIC waves dominate.

  6. Magnetic anisotropy of Ni/Cr multilayers

    International Nuclear Information System (INIS)

    Kang, S.; Xia, H.

    1997-01-01

    The magnetic anisotropy of Ni/Cr multilayers has been investigated by using vibrating sample magnetometer (VSM) and ferromagnetic resonance techniques (FMR). The FMR spectra are obtained as a function of the orientation of the applied magnetic field from in-plane to out-of-plane. The results are fitted theoretically to determine the magnetic anisotropy. From VSM and FMR, a positive value for Ni/Cr interface anisotropy is obtained, which favours a perpendicular easy axis. The possible mechanism for the perpendicular anisotropy has been discussed and it may be attributed to the magnetostriction, caused by intrinsic stress due to lattice mismatch. (orig.). With 005 figs., 001 tabs

  7. Influence of an uniaxial stress on point defects

    International Nuclear Information System (INIS)

    Beuneu, B.

    1984-03-01

    We study two effects of an elastic external uniaxial stress on point defects (created by electron irradiation): 1.- We measure the linear variation of their resistivity rhosub(D) under the elastic strain epsilon in Copper. It gives the specific elastoresistivity (E.R.S.) chisub(D)=delta rhosub(D)/epsilon. With the help of the results of VON STEBUT (fast neutrons) we show that the E.R.S. is characteristic of a defect and of its configuration. 2.- By means of resistivity measurements in molybdenum, we observe a paraelastic phenomenon. It is thermally activated (νsub(0) approximately= 10 12 s -1 and E approximately= 72 meV) and we attribute it to the reorientation of a dumbell interstitial under the uniaxial stress. The resistivity of this dumbbell is higher along its axis than perpendicularly to it. We have completed these results with some configuration energy calculations for the dumbbell and with a simple kinetic model [fr

  8. Theoretical study of Cherenkov radiation emission in anisotropic uniaxial crystals

    Energy Technology Data Exchange (ETDEWEB)

    Delbart, A; Derre, J

    1996-04-01

    A theoretical review of the Cherenkov radiation emission in uniaxial crystals is presented. The formalism of C. Muzicar in terms of energetic properties of the emitted waves are corrected. This formalism is used to simulate the Cherenkov radiation emission in a strongly birefringent sodium nitrate crystal (NaNO{sub 3}) and to investigate the consequences of the slight anisotropy of sapphire (Al{sub 2}O{sub 3}) on the design of the Optical Trigger. (author). 12 refs. Submitted to Physical Review, D (US).

  9. Experimental and numerical study on mechanical properties of aluminum alloy under uniaxial tensile test

    Directory of Open Access Journals (Sweden)

    O. Daghfas

    2017-01-01

    Full Text Available The main objective is to model the behavior of 7075 aluminum alloy and built an experimental database to identify the model parameters. The first part of the paper presents an experimental database on 7075 aluminum alloy. Thus, uniaxial tensile tests are carried in three loading directions relative to the rolling direction, knowing that the fatigue of aircraft structures is traditionally managed based on the assumption of uniaxial loads. From experimental database, the mechanical properties are extracted, particularly the various fractures owing to pronounced anisotropy relating to material. In second part, plastic anisotropy is then modeled using the identification strategy which depends on yield criteria, hardening law and evolution law. In third part, a comparison with experimental data shows that behavior model can successfully describe the anisotropy of the Lankford coefficient.

  10. Anisotropy of domain wall resistance

    Science.gov (United States)

    Viret; Samson; Warin; Marty; Ott; Sondergard; Klein; Fermon

    2000-10-30

    The resistive effect of domain walls in FePd films with perpendicular anisotropy was studied experimentally as a function of field and temperature. The films were grown directly on MgO substrates, which induces an unusual virgin magnetic configuration composed of 60 nm wide parallel stripe domains. This allowed us to carry out the first measurements of the anisotropy of domain wall resistivity in the two configurations of current perpendicular and parallel to the walls. At 18 K, we find 8.2% and 1.3% for the domain wall magnetoresistance normalized to the wall width (8 nm) in these two respective configurations. These values are consistent with the predictions of Levy and Zhang.

  11. Novel surface anisotropy term in the FMR spectra of amorphous microwires

    International Nuclear Information System (INIS)

    Gutowski, M.W.; Zuberek, R.; Zhukov, A.

    2004-01-01

    Some recent publications on ferromagnetic resonance in amorphous wires mention presumably a new kind of anisotropy, called there circumferential anisotropy, as an explanation of various observed spectral features. In this paper, we argue that there is no special reason to speak of the new kind of anisotropy, since the observed spectra can be well described in terms of more traditional uniaxial and surface anisotropies alone

  12. Skyrmion robustness in noncentrosymmetric magnets with axial symmetry: The role of anisotropy and tilted magnetic fields

    Science.gov (United States)

    Leonov, A. O.; Kézsmárki, I.

    2017-12-01

    We investigate the stability of Néel skyrmions against tilted magnetic fields in polar magnets with uniaxial anisotropy ranging from easy-plane to easy-axis type. We construct the corresponding phase diagrams and investigate the internal structure of skewed skyrmions with displaced cores. We find that moderate easy-plane anisotropy increases the stability range of Néel skyrmions for fields along the symmetry axis, while moderate easy-axis anisotropy enhances their robustness against tilted magnetic fields. We stress that the direction along which the skyrmion cores are shifted depends on the symmetry of the underlying crystal lattice. The cores of Néel skyrmions, realized in polar magnets with Cn v symmetry, are displaced either along or opposite to the off-axis (in-plane) component of the magnetic field depending on the rotation sense of the magnetization, dictated by the sign of the Dzyaloshinskii constant. The core shift of antiskyrmions, present in noncentrosymmetric magnets with D2 d symmetry, depends on the in-plane orientation of the magnetic field and can be parallel, antiparallel, or perpendicular to it. We argue that the role of anisotropy in magnets with axially symmetric crystal structure is different from that in cubic helimagnets. Our results can be applied to address recent experiments on polar magnets with C3 v symmetry, GaV4S8 and GaV4Se8 , and Mn1.4Pt0.9Pd0.1Sn with D2 d symmetry.

  13. Thickness and angular dependent magnetic anisotropy of La0.67Sr0.33MnO3 thin films by Vectorial Magneto Optical Kerr Magnetometry

    Science.gov (United States)

    Chaluvadi, S. K.; Perna, P.; Ajejas, F.; Camarero, J.; Pautrat, A.; Flament, S.; Méchin, L.

    2017-10-01

    We investigate the in-plane magnetic anisotropy in La0.67Sr0.33MnO3 thin films grown on SrTiO3 (001) substrate using angular dependent room temperature Vectorial Magneto-Optical Kerr Magnetometry. The experimental data reveals that the magnetic anisotropy symmetry landscape significantly changes depending upon the strain and thickness. At low film thickness (12 and 25 nm) the dominant uniaxial anisotropy is due to interface effects, step edges due to mis-cut angle of SrTiO3 substrate. At intermediate thickness, the magnetic anisotropy presents a competition between magnetocrystalline (biaxial) and substrate step induced (uniaxial) anisotropy. Depending upon their relative strengths, a profound biaxial or uniaxial or mixed anisotropy is favoured. Above the critical thickness, magnetocrystalline anisotropy dominates all other effects and shows a biaxial anisotropy.

  14. Magnetic and structural properties of L1{sub 1} type CoPt-C ordered alloy perpendicular films as a function of C content

    Energy Technology Data Exchange (ETDEWEB)

    Shimatsu, T; Kataoka, H; Aoi, H [Research Institute of Electrical Communication, Tohoku University, Sendai, 980-8577 (Japan); Sato, H; Okamoto, S; Kitakami, O, E-mail: shimatsu@riec.tohoku.ac.j [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, 980-8577 (Japan)

    2010-01-01

    Magnetic and structural properties of L1{sub 1} type (Co{sub 0.5}Pt{sub 0.5}){sub 100-X}-C{sub X} ordered alloy perpendicular films, fabricated on 2.5 inch size glass disks by sputter deposition, were examined as a function of C content, X. L1{sub 1} type Co{sub 0.5}Pt{sub 0.5}-C polycrystalline films (10 nm thickness), with <111> axis (the easy axis) perpendicular to the film plane, were successfully fabricated even for a 30 vol% C content. Structural analysis indicated the segregation of C to the grain boundaries. Uniaxial magnetic anisotropy, K{sub u}, of Co{sub 0.5}Pt{sub 0.5} films without C addition was relatively low, about 1.5x10{sup 7} erg/cm{sup 3} under the present deposition conditions. However, the addition of 5 vol.% C to Co-Pt films enhanced the ordering, resulting in an increase in K{sub u} to around 2.5 x10{sup 7} erg/cm{sup 3}. A further increase in C content reduced K{sub u}; however, K{sub u} maintained a relatively large value of about 1.8x10{sup 7} erg/cm{sup 3} even for a 20vol% C content, without degrading the easy axis orientation perpendicular to the film plane. Experimental results demonstrated the potential of the L1{sub 1} type Co{sub 0.5}Pt{sub 0.5}-C films for use in granular media applications, due to their very high K{sub u}, the relatively low fabrication temperature, and good controllability of the grain orientation.

  15. Assessment of velocity anisotropy in rocks

    Czech Academy of Sciences Publication Activity Database

    Lokajíček, Tomáš; Goel, R. K.; Rudajev, Vladimír; Dwivedi, R.D.

    2013-01-01

    Roč. 57, January (2013), s. 142-152 ISSN 1365-1609 R&D Projects: GA ČR(CZ) GA205/08/0676; GA AV ČR IAA300130906; GA ČR(CZ) GAP104/12/0915 Institutional research plan: CEZ:AV0Z30130516 Keywords : elastic anisotropy * acoustic emission * uniaxial loading * hydrostatic loading Subject RIV: DB - Geology ; Mineralogy Impact factor: 1.424, year: 2013

  16. Tuning the Magnetic Anisotropy at a Molecule-Metal Interface

    DEFF Research Database (Denmark)

    Bairagi, K.; Bellec, A.; Repain, V.

    2015-01-01

    We demonstrate that a C60 overlayer enhances the perpendicular magnetic anisotropy of a Co thin film, inducing an inverse spin reorientation transition from in plane to out of plane. The driving force is the C60/Co interfacial magnetic anisotropy that we have measured quantitatively in situ...

  17. Saturation and oscillation of current in semiconductors subjected to uniaxial deformation

    International Nuclear Information System (INIS)

    Zdebskii, A.P.; Olikh, Yu.A.; Savchuk, A.U.

    1985-01-01

    The influence of an external uniaxial deformation on the saturation and oscillations of current in photosensitive CdS monocrystals is investigated. The specimens were subjected to uniaxial pressure up to 6 x 10 7 N/m 2 , the pressure being either parallel or perpendicular to the c axis in CdS. With application of external pressure, the shape of current oscillations and their amplitude changed. In the case where the pressure was perpendicular to the direction of current I, the amplitude of oscillations and the saturation depth of the volt-ampere characteristic, VAC, were increased. With pressure being parallel to the current direction, the reverse phenomenon was observed, i.e. the efficiency of the acousto-electronic interaction was reduced

  18. Read/write performance of perpendicular double-layered cylindrical media

    International Nuclear Information System (INIS)

    Yamada, H.; Shimatsu, T.; Watanabe, I.; Tsuchiyama, R.; Aoi, H.; Muraoka, H.; Nakamura, Y.

    2005-01-01

    A cylindrical magnetic storage system using perpendicular double-layered media has been developed. CoCrTa/CoZrNb deposited on a rotating cylindrical substrate shows perpendicular anisotropy and magnetic properties, which have almost the same characteristics as conventional disk-media. The fundamental read/write characteristics of perpendicular double-layered cylindrical media were measured using a single-pole-type (SPT) writer with a sliding-contact-type slider and a merged giant magneto-resistive (GMR) reader with a one-pad-type slider designed for use with cylindrical media. Preliminary studies for improving the characteristics of the recording layer are also described

  19. Tuning giant anomalous Hall resistance ratio in perpendicular Hall balance

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, J. Y.; Yang, G. [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China); State Key Laboratory of Magnetism, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Wang, S. G., E-mail: sgwang@iphy.ac.cn, E-mail: ghyu@mater.ustb.edu.cn [State Key Laboratory of Magnetism, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Liu, J. L. [State Key Laboratory of Magnetism, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Department of Physics, Beijing University of Aeronautics and Astronautics, Beijing 100191 (China); Wang, R. M. [Department of Physics, Beijing University of Aeronautics and Astronautics, Beijing 100191 (China); Amsellem, E.; Kohn, A. [Department of Materials Engineering, Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beer-Sheva 84105 (Israel); Yu, G. H., E-mail: sgwang@iphy.ac.cn, E-mail: ghyu@mater.ustb.edu.cn [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China)

    2015-04-13

    Anomalous Hall effect at room temperature in perpendicular Hall balance with a core structure of [Pt/Co]{sub 4}/NiO/[Co/Pt]{sub 4} has been tuned by functional CoO layers, where [Pt/Co]{sub 4} multilayers exhibit perpendicular magnetic anisotropy. A giant Hall resistance ratio up to 69 900% and saturation Hall resistance (R{sub S}{sup P}) up to 2590 mΩ were obtained in CoO/[Pt/Co]{sub 4}/NiO/[Co/Pt]{sub 4}/CoO system, which is 302% and 146% larger than that in the structure without CoO layers, respectively. Transmission electron microscopy shows highly textured [Co/Pt]{sub 4} multilayers and oxide layers with local epitaxial relations, indicating that the crystallographic structure has significant influence on spin dependent transport properties.

  20. Ground-state phase diagram of an (S, S') = (1, 2) spin-alternating chain with competing single-ion anisotropies

    International Nuclear Information System (INIS)

    Tonegawa, T; Okamoto, K; Sakai, T; Kaburagi, M

    2009-01-01

    Employing various numerical methods, we determine the ground-state phase diagram of an (S, S') = (1, 2) spin-alternating chain with antiferromagnetic nearest-neighboring exchange interactions and uniaxial single-ion anisotropies. The resulting phase diagram consists of eight kinds of phases including two phases which accompany the spontaneous breaking of the translational symmetry and a ferrimagnetic phase in which the ground-state magnetization varies continuously with the uniaxial single-ion anisotropy constants for the S=1 and S =2 spins. The appearance of these three phases is attributed to the competition between the uniaxial single-ion anisotropies of both spins.

  1. Magnetization measurement of single La0.67Ca0.33MnO3 nanotubes in perpendicular magnetic fields using a micromechanical torsional oscillator

    International Nuclear Information System (INIS)

    Antonio, D.; Dolz, M.I.; Pastoriza, H.

    2010-01-01

    Using a silicon micromechanical resonator as a sensitive magnetometer, the authors have studied both experimentally and theoretically the magnetic behavior of two isolated ferromagnetic nanotubes of perovskite La 0.67 Ca 0.33 MnO 3 . The article investigates the specific configuration where a magnetic field H is applied perpendicular to the magnetic easy axis of an isolated nanotube characterized by an uniaxial anisotropy constant K. In this situation, the magnetization M reduces the effective elastic constant k M of the resonator. This softening of the mechanical system is opposed to the hardening effect of M observed in a previous work, where H was applied parallel to the easy axis. Moreover, in this magnetic field configuration two distinct magnetization regimes are manifested, depending on the magnitude of H. For H>>2K/M the magnetization is almost parallel to the applied magnetic field and for H<<2K/M it is almost parallel to the easy axis of the nanotube. At a certain value of H there is a sharp transition from one regime to the other, accompanied by a peak in the energy dissipation.

  2. Magnetic and transport properties of single and double perpendicular magnetic tunnel junctions

    International Nuclear Information System (INIS)

    Cuchet, Lea

    2015-01-01

    Due to their advantageous properties in terms of data retention, storage density and critical current density for Spin Transfer Torque (STT) switching, the magnetic tunnel junctions with perpendicular anisotropy have become predominant in the developments for MRAM applications. The aim of this thesis is to improve the anisotropy and transport properties of such structures and to realize even more complex stacks such as perpendicular double junctions. Studies on the magnetic properties and Tunnel Magnetoresistance (TMR) measurements showed that to optimize the performances of the junctions, all the thicknesses of the different layers constituting the stack have to be adapted. To guaranty both a large TMR as well a strong perpendicular anisotropy, compromises are most of the time needed. Studies as a function of magnetic thickness enabled to extract the saturation magnetization, the critical thickness and the magnetic dead layer thickness both in the bottom reference and the top storage layer in structures capped with Ta. This type of junction could be tested electrically after patterning the sample into nano-pillars. Knowing that perpendicular anisotropy mostly arises at the metal/oxide interface, the Ta capping layer was replaced by a MgO one, leading to a huge increase in the anisotropy of the free layer. A second top reference was then added on such a stack to create functional perpendicular double junctions. CoFeB/insertion/CoFeB synthetic antiferromagnetic storage layers could be developed and were proved to be stable enough to replace the standard Co/Pt-based reference layers. (author) [fr

  3. Studies in perpendicular magnetic recording

    Science.gov (United States)

    Valcu, Bogdan F.

    This dissertation uses both micromagnetic simulation and analytical methods to analyze several aspects of a perpendicular recording system. To increase the head field amplitude, the recording layer is grown on top of a soft magnetic layer (keeper). There is concern about the ability of the keeper to conduct the magnetic flux from the head at high data rates. We compute numerically the magnetization motion of the soft underlayer during the reversal process. Generation of non-linear spin waves characterizes the magnetization dynamics in the keeper, the spins are oscillating with a frequency higher than that of the reversal current. However, the recording field applied to the data layer follows the time dependence of the input wave form. The written transition shape is determined by the competition between the head field gradient and the demagnetizing field gradient. An analytical slope model that takes into consideration the angular orientation of the applied field is used to estimate the transition parameter; agreement is shown with the micromagnetic results. On the playback side, the reciprocity principle is applied to calculate the read out signal from a single magnetic transition in the perpendicular medium. The pulse shape is close to an error-function, going through zero when the sensor is above the transition center and decaying from the peak to an asymptotic value when the transition center is far away. Analytical closed forms for both the slope in the origin and the asymptotic value show the dependence on the recording geometry parameters. The Signal-to-Noise Ratio is calculated assuming that the noise is dominated by the medium jitter. To keep the SNR at a readable level while increasing the areal density, the average magnetic grain diameter must decrease; consequently grain size fluctuations will affect the thermal decay. We performed Transmission Electron Microscopy measurements and observed differences in the grain size distribution between various types

  4. Notch effects in uniaxial tension specimens

    International Nuclear Information System (INIS)

    Delph, T.J.

    1979-03-01

    Results of a literature survey on the effect of notches on the time-dependent failure of uniaxial tension specimens at elevated temperatures are presented. Particular attention is paid to the failure of notched specimens containing weldments

  5. Flow-induced elastic anisotropy of metallic glasses

    International Nuclear Information System (INIS)

    Sun, Y.H.; Concustell, A.; Carpenter, M.A.; Qiao, J.C.; Rayment, A.W.; Greer, A.L.

    2016-01-01

    As-cast bulk metallic glasses are isotropic, but anisotropy can be induced by thermomechanical treatments. For example, the diffraction halo in the structure function S(Q) observed in transmission becomes elliptical (rather than circular) after creep in uniaxial tension or compression. Published studies associate this with frozen-in anelastic strain and bond-orientational anisotropy. Results so far are inconsistent on whether viscoplastic flow of metallic glasses can induce anisotropy. Preliminary diffraction data suggest that the anisotropy, if any, is very low, while measurements of the elastic properties suggest that there is induced anisotropy, opposite in sign to that due to anelastic strain. We study three bulk metallic glasses, Ce 65 Al 10 Cu 20 Co 5 , La 55 Ni 10 Al 35 , and Pd 40 Ni 30 Cu 10 P 20 . By using resonant ultrasound spectroscopy to determine the full elasticity tensor, the effects of relaxation and rejuvenation can be reliably separated from uniaxial anisotropy (of either sign). The effects of viscoplastic flow in tension are reported for the first time. We find that viscoplastic flow of bulk metallic glasses, particularly in tension, can induce significant anisotropy that is distinct from that associated with frozen-in anelastic strain. The conditions for inducing such anisotropy are explored in terms of the Weissenberg number (ratio of relaxation times for primary relaxation and for shear strain rate). There is a clear need for further work to characterize the structural origins of flow-induced anisotropy and to explore the prospects for improved mechanical and other properties through induced anisotropy.

  6. Control of the magnetic in-plane anisotropy in off-stoichiometric NiMnSb

    International Nuclear Information System (INIS)

    Gerhard, F.; Schumacher, C.; Gould, C.; Molenkamp, L. W.

    2014-01-01

    NiMnSb is a ferromagnetic half-metal which, because of its rich anisotropy and very low Gilbert damping, is a promising candidate for applications in information technologies. We have investigated the in-plane anisotropy properties of thin, molecular beam epitaxy-grown NiMnSb films as a function of their Mn concentration. Using ferromagnetic resonance to determine the uniaxial and four-fold anisotropy fields, (2K U )/(M s ) and (2K 1 )/(M s ) , we find that a variation in composition can change the strength of the four-fold anisotropy by more than an order of magnitude and cause a complete 90° rotation of the uniaxial anisotropy. This provides valuable flexibility in designing new device geometries

  7. Controlling the anisotropy and domain structure with oblique deposition and substrate rotation

    Directory of Open Access Journals (Sweden)

    N. Chowdhury

    2014-02-01

    Full Text Available Effect of substrate rotation on anisotropy and domain structure for a thin ferromagnetic film has been investigated in this work. For this purpose Co films with 10 nm thickness have been prepared by sputtering with oblique angle of incidence for various substrate rotations. This method of preparation induces a uniaxial anisotropy due to shadow deposition effect. The magnetization reversal is studied by magneto-optic Kerr effect (MOKE based microscope in the longitudinal geometry. The Co films prepared by rotating the substrate with 10 and 20 rpm weakens the anisotropy but does not completely give isotropic films. But this leads to high dispersion in local grain anisotropy resulting in ripple and labyrinth domains. It is observed that the substrate rotation has moderate effect on uniaxial anisotropy but has significant effect on the magnetization reversal process and the domain structure.

  8. Magnetic anisotropy in (Ga,Mn)As: Influence of epitaxial strain and hole concentration

    Science.gov (United States)

    Glunk, M.; Daeubler, J.; Dreher, L.; Schwaiger, S.; Schoch, W.; Sauer, R.; Limmer, W.; Brandlmaier, A.; Goennenwein, S. T. B.; Bihler, C.; Brandt, M. S.

    2009-05-01

    We present a systematic study on the influence of epitaxial strain and hole concentration on the magnetic anisotropy in (Ga,Mn)As at 4.2 K. The strain was gradually varied over a wide range from tensile to compressive by growing a series of (Ga,Mn)As layers with 5% Mn on relaxed graded (In,Ga)As/GaAs templates with different In concentration. The hole density, the Curie temperature, and the relaxed lattice constant of the as-grown and annealed (Ga,Mn)As layers turned out to be essentially unaffected by the strain. Angle-dependent magnetotransport measurements performed at different magnetic-field strengths were used to probe the magnetic anisotropy. The measurements reveal a pronounced linear dependence of the uniaxial out-of-plane anisotropy on both strain and hole density. Whereas the uniaxial and cubic in-plane anisotropies are nearly constant, the cubic out-of-plane anisotropy changes sign when the magnetic easy axis flips from in-plane to out-of-plane. The experimental results for the magnetic anisotropy are quantitatively compared with calculations of the free energy based on a mean-field Zener model. Almost perfect agreement between experiment and theory is found for the uniaxial out-of-plane and cubic in-plane anisotropy parameters of the as-grown samples. In addition, magnetostriction constants are derived from the anisotropy data.

  9. Nano-patterning of perpendicular magnetic recording media by low-energy implantation of chemically reactive ions

    International Nuclear Information System (INIS)

    Martin-Gonzalez, M.S.; Briones, F.; Garcia-Martin, J.M.; Montserrat, J.; Vila, L.; Faini, G.; Testa, A.M.; Fiorani, D.; Rohrmann, H.

    2010-01-01

    Magnetic nano-patterning of perpendicular hard disk media with perpendicular anisotropy, but preserving disk surface planarity, is presented here. Reactive ion implantation is used to locally modify the chemical composition (hence the magnetization and magnetic anisotropy) of the Co/Pd multilayer in irradiated areas. The procedure involves low energy, chemically reactive ion irradiation through a resist mask. Among N, P and As ions, P are shown to be most adequate to obtain optimum bit density and topography flatness for industrial Co/Pd multilayer media. The effect of this ion contributes to isolate perpendicular bits by destroying both anisotropy and magnetic exchange in the irradiated areas. Low ion fluences are effective due to the stabilization of atomic displacement levels by the chemical effect of covalent impurities.

  10. Bidirectional recording performance of a perpendicular evaporated Co-CoO tape

    Energy Technology Data Exchange (ETDEWEB)

    Motohashi, K. [Sony Corporation, 3-4-1 Sakuragi, Tagajo-shi, Miyagi 985-0842 (Japan)], E-mail: Kazunari.Motohashi@jp.sony.com; Ikeda, N.; Sato, T.; Shiga, D.; Ono, H.; Onodera, S. [Sony Corporation, 3-4-1 Sakuragi, Tagajo-shi, Miyagi 985-0842 (Japan)

    2008-11-15

    It is the first report on the recording performance of a perpendicular metal evaporated (ME) tape measured with a giant magnetoresistive head. To solve the application difficulty of oblique evaporated tape media to linear scan tape systems, a perpendicular evaporated Co-CoO tape was proposed instead. The prepared sample showed perpendicular anisotropy with coercivity of 107.3 kA/m, M{sub r}t of 3.9 mA and squareness of 0.25. Identical recording characteristics were obtained for both head-media moving directions, which enables the application of perpendicular evaporated Co-CoO tape to linear scan tape systems. The better carrier-to-noise ratio was also confirmed by comparison with a current advanced product of metal particulate tape, which can realize the higher recording density of linear scan tape systems using ME tape.

  11. Bidirectional recording performance of a perpendicular evaporated Co-CoO tape

    International Nuclear Information System (INIS)

    Motohashi, K.; Ikeda, N.; Sato, T.; Shiga, D.; Ono, H.; Onodera, S.

    2008-01-01

    It is the first report on the recording performance of a perpendicular metal evaporated (ME) tape measured with a giant magnetoresistive head. To solve the application difficulty of oblique evaporated tape media to linear scan tape systems, a perpendicular evaporated Co-CoO tape was proposed instead. The prepared sample showed perpendicular anisotropy with coercivity of 107.3 kA/m, M r t of 3.9 mA and squareness of 0.25. Identical recording characteristics were obtained for both head-media moving directions, which enables the application of perpendicular evaporated Co-CoO tape to linear scan tape systems. The better carrier-to-noise ratio was also confirmed by comparison with a current advanced product of metal particulate tape, which can realize the higher recording density of linear scan tape systems using ME tape

  12. Friction Anisotropy with Respect to Topographic Orientation

    Science.gov (United States)

    Yu, Chengjiao; Wang, Q. Jane

    2012-01-01

    Friction characteristics with respect to surface topographic orientation were investigated using surfaces of different materials and fabricated with grooves of different scales. Scratching friction tests were conducted using a nano-indentation-scratching system with the tip motion parallel or perpendicular to the groove orientation. Similar friction anisotropy trends were observed for all the surfaces studied, which are (1) under a light load and for surfaces with narrow grooves, the tip motion parallel to the grooves offers higher friction coefficients than does that perpendicular to them, (2) otherwise, equal or lower friction coefficients are found under this motion. The influences of groove size relative to the diameter of the mating tip (as a representative asperity), surface contact stiffness, contact area, and the characteristic stiction length are discussed. The appearance of this friction anisotropy is independent of material; however, the boundary and the point of trend transition depend on material properties. PMID:23248751

  13. Experimental investigation of ultrasonic velocity anisotropy in ...

    Indian Academy of Sciences (India)

    Permanent link: https://www.ias.ac.in/article/fulltext/pram/077/02/0345-0355. Keywords. Magnetic fluids; ultrasonic wave; sound velocity; anisotropy. Abstract. Magnetic field-induced dispersion of ultrasonic velocity in a Mn0.7Zn0.3Fe2O4 fluid (applied magnetic field is perpendicular to the ultrasonic propagation vector) is ...

  14. Giant magnetic anisotropy and tunnelling of the magnetization in Li2(Li_{1-x}Fe_x)N

    OpenAIRE

    Jesche, A.; McCallum, R. W.; Thimmaiah, S.; Jacobs, J. L.; Taufour, V.; Kreyssig, A.; Houk, R. S.; Bud'ko, S. L.; Canfield, P. C.

    2014-01-01

    Large magnetic anisotropy and coercivity are key properties of functional magnetic materials and are generally associated with rare earth elements. Here we show an extreme, uniaxial magnetic anisotropy and the emergence of magnetic hysteresis in Li2(Li1-xFex)N. An extrapolated, magnetic anisotropy field of 220 Tesla and a coercivity field of over 11 Tesla at 2 Kelvin outperform all known hard-ferromagnets and single-molecule magnets (SMMs). Steps in the hysteresis loops and relaxation phenome...

  15. A general perspective on the magnetization reversal in cylindrical soft magnetic nanowires with dominant shape anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Kuncser, A. [National Institute of Materials Physics, PO Box MG-7, 077125 Bucharest-Magurele (Romania); University of Bucharest, Faculty of Physics, PO Box MG-11, 077125 Bucharest-Magurele (Romania); Antohe, S. [University of Bucharest, Faculty of Physics, PO Box MG-11, 077125 Bucharest-Magurele (Romania); Kuncser, V., E-mail: kuncser@infim.ro [National Institute of Materials Physics, PO Box MG-7, 077125 Bucharest-Magurele (Romania)

    2017-02-01

    Peculiarities of the magnetization reversal process in cylindrical Ni-Cu soft magnetic nanowires with dominant shape anisotropy are analyzed via both static and time dependent micromagnetic simulations. A reversible process involving a coherent-like spin rotation is always observed for magnetic fields applied perpendicularly to the easy axis whereas nucleation of domain walls is introduced for fields applied along the easy axis. Simple criteria for making distinction between a Stoner-Wohlfarth type rotation and a nucleation mechanism in systems with uniaxial magnetic anisotropy are discussed. Superposed reversal mechanisms can be in action for magnetic fields applied at arbitrary angles with respect to the easy axis within the condition of an enough strong axial component required by the nucleation. The dynamics of the domain wall, involving two different stages (nucleation and propagation), is discussed with respect to initial computing conditions and orientations of the magnetic field. A nucleation time of about 3 ns and corkscrew domain walls propagating with a constant velocity of about 150 m/s are obtained in case of Ni-Cu alloy (Ni rich side) NWs with diameters of 40 nm and high aspect ratio. - Highlights: • The formation and the dynamics of the domain walls in magnetic nanowires have been studied by micromagnetic simulations. • Simple criteria for making distinction between Stoner-Wohlfarth type and nucleation mechanisms in nanowires were discussed. • Corkscrew domain walls or quasi-coherent spin rotation may be induced depending on the field orientation. • The nucleation time was estimated at 3 ns and the wall velocity at 150 m/s. • A simple way for tuning the wall velocity in such systems was mentioned.

  16. Capping layer-tailored interface magnetic anisotropy in ultrathin Co2FeAl films

    International Nuclear Information System (INIS)

    Belmeguenai, M.; Zighem, F.; Chérif, S. M.; Gabor, M. S.; Petrisor, T.; Tiusan, C.

    2015-01-01

    Co 2 FeAl (CFA) thin films of various thicknesses (2 nm ≤ d ≤ 50 nm) have been grown on (001) MgO single crystal substrates and then capped with Cr, V, and Ta. Their magnetic and structural properties have been studied by x-ray diffraction (XRD), vibrating sample magnetometry, and broadband microstrip ferromagnetic resonance (MS-FMR). The XRD revealed that the films are epitaxial with the cubic [001] CFA axis normal to the substrate plane and that the chemical order varies from the B2 phase to the A2 phase when decreasing the thickness. The deduced lattice parameters showed that the Cr-capped films exhibit a larger tetragonal distortion, as compared with the films capped with V or Ta. The presence of magnetic dead layers has been observed in CFA samples capped with V and Ta but not in the case of the Cr-capped ones. The effective magnetization, deduced from the fit of MS-FMR measurements, increases (decreases) linearly with the CFA inverse thickness (1/d) for the Cr-capped (Ta-capped) films while it is constant for the V-capped ones. This allows quantifying the perpendicular surface anisotropy coefficients of −0.46 erg/cm 2 and 0.74 erg/cm 2 for Cr and Ta-capped films, respectively. Moreover, the fourfold and the uniaxial anisotropy fields, measured in these films, showed different trends with a respect to the CFA inverse thickness. This allows inferring that a non-negligible part of the fourfold magnetocrystalline term is of interfacial origin

  17. Temperature dependence of microwave oscillations in magnetic tunnel junctions with a perpendicularly magnetized free layer

    International Nuclear Information System (INIS)

    Guo, Peng; Feng, Jiafeng; Wei, Hongxiang; Han, Xiufeng; Fang, Bin; Zhang, Baoshun; Zeng, Zhongming

    2015-01-01

    We experimentally study the temperature dependence of the spin-transfer-torque-induced microwave oscillations in MgO-based magnetic tunnel junction nanopillars with a perpendicularly magnetized free layer. We demonstrate that the oscillation frequency increases rapidly with decreasing temperature, which is mainly ascribed to the temperature dependence of both the saturation magnetization and the perpendicular magnetic anisotropy. We also find that a strong temperature dependence of the output power while a nonmonotonic temperature dependence of spectral linewidth are maintained for a constant dc bias in measured temperature range. Possible mechanisms leading to the different dependences of oscillation frequency, output power, and linewidth are discussed

  18. Stable evaluation of Green's functions in cylindrically stratified regions with uniaxial anisotropic layers

    Science.gov (United States)

    Moon, H.; Donderici, B.; Teixeira, F. L.

    2016-11-01

    We present a robust algorithm for the computation of electromagnetic fields radiated by point sources (Hertzian dipoles) in cylindrically stratified media where each layer may exhibit material properties (permittivity, permeability, and conductivity) with uniaxial anisotropy. Analytical expressions are obtained based on the spectral representation of the tensor Green's function based on cylindrical Bessel and Hankel eigenfunctions, and extended for layered uniaxial media. Due to the poor scaling of these eigenfunctions for extreme arguments and/or orders, direct numerical evaluation of such expressions can produce numerical instability, i.e., underflow, overflow, and/or round-off errors under finite precision arithmetic. To circumvent these problems, we develop a numerically stable formulation through suitable rescaling of various expressions involved in the computational chain, to yield a robust algorithm for all parameter ranges. Numerical results are presented to illustrate the robustness of the formulation including cases of practical interest.

  19. Stable evaluation of Green's functions in cylindrically stratified regions with uniaxial anisotropic layers

    Energy Technology Data Exchange (ETDEWEB)

    Moon, H., E-mail: haksu.moon@gmail.com [ElectroScience Laboratory, The Ohio State University, Columbus, OH 43212 (United States); Donderici, B., E-mail: burkay.donderici@halliburton.com [Sensor Physics & Technology, Halliburton Energy Services, Houston, TX 77032 (United States); Teixeira, F.L., E-mail: teixeira@ece.osu.edu [ElectroScience Laboratory, The Ohio State University, Columbus, OH 43212 (United States)

    2016-11-15

    We present a robust algorithm for the computation of electromagnetic fields radiated by point sources (Hertzian dipoles) in cylindrically stratified media where each layer may exhibit material properties (permittivity, permeability, and conductivity) with uniaxial anisotropy. Analytical expressions are obtained based on the spectral representation of the tensor Green's function based on cylindrical Bessel and Hankel eigenfunctions, and extended for layered uniaxial media. Due to the poor scaling of these eigenfunctions for extreme arguments and/or orders, direct numerical evaluation of such expressions can produce numerical instability, i.e., underflow, overflow, and/or round-off errors under finite precision arithmetic. To circumvent these problems, we develop a numerically stable formulation through suitable rescaling of various expressions involved in the computational chain, to yield a robust algorithm for all parameter ranges. Numerical results are presented to illustrate the robustness of the formulation including cases of practical interest.

  20. Determination of the Fe magnetic anisotropies and the CoO frozen spins in epitaxial CoO/Fe/Ag(001)

    Energy Technology Data Exchange (ETDEWEB)

    Meng, J. Li, Y.; Park, J. S.; Jenkins, C. A.; Arenholz, E.; Scholl, A.; Tan, A.; Son, H.; Zhao, H. W.; Hwang, Chanyong; Qiu, Z. Q.

    2011-04-28

    CoO/Fe/Ag(001) films were grown epitaxially and studied by X-ray Magnetic Circular Dichroism (XMCD) and X-ray Magnetic Linear Dichroism (XMLD). After field cooling along the Fe[100] axis to 80 K, exchange bias, uniaxial anisotropy, and 4-fold anisotropy of the films were determined by hysteresis loop and XMCD measurements by rotating the Fe magnetization within the film plane. The CoO frozen spins were determined by XMLD measurement as a function of CoO thickness.We find that among the exchange bias, uniaxial anisotropy, and 4-fold anisotropy, only the uniaxial magnetic anisotropy follows thickness dependence of the CoO frozen spins.

  1. Correction between B and H, and the analysis of the magnetization into uniaxial superconductor in the limit at large values of B

    International Nuclear Information System (INIS)

    Oliveira, I.G. de.

    1994-04-01

    Using the London theory, a correction is obtained between the direction of the magnetic induction B and the applied magnetic field H in superconductors with uniaxial anisotropy when the Ginsburg-Landau constant is not so large. One analysis of the magnetization as function of angle α is made. (author). 5 refs, 2 figs

  2. Correction between B and H, and the analysis of the magnetization into uniaxial superconductor in the limit at large values of B

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, I.G. de

    1994-04-01

    Using the London theory, a correction is obtained between the direction of the magnetic induction B and the applied magnetic field H in superconductors with uniaxial anisotropy when the Ginsburg-Landau constant is not so large. One analysis of the magnetization as function of angle {alpha} is made. (author). 5 refs, 2 figs.

  3. Large Friction Anisotropy of a Polydiacetylene Monolayer

    International Nuclear Information System (INIS)

    Burns, A.R.; Carpick, R.W.; Sasaki, D.Y.

    1999-01-01

    Friction force microscopy measurements of a polydiacetylene monolayer film reveal a 300% friction anisotropy that is correlated with the film structure. The film consists of a monolayer of the red form of N-(2-ethanol)- 10,12 pentacosadiynamide, prepared on a Langmuir trough and deposited on a mica substrate. As confirmed by atomic force microscopy and fluorescence microscopy, the monolayer consists of domains of linearly oriented conjugated backbones with pendant hydrocarbon side chains above and below the backbones. Maximum friction occurs when the sliding direction is perpendicular to the backbone. We propose that the backbones impose anisotropic packing of the hydrocarbon side chains which leads to the observed friction anisotropy. Friction anisotropy is therefore a sensitive, optically-independent indicator of polymer backbone direction and monolayer structural properties

  4. Domain wall motion in ferromagnetic systems with perpendicular magnetization

    International Nuclear Information System (INIS)

    Szambolics, H.; Toussaint, J.-Ch.; Marty, A.; Miron, I.M.; Buda-Prejbeanu, L.D.

    2009-01-01

    Although we lack clear experimental evidence, apparently out-of-plane magnetized systems are better suited for spintronic applications than the in-plane magnetized ones, mainly due to the smaller current densities required for achieving domain wall motion. [Co/Pt] multilayers belong to the first category of materials, the out-of-plane magnetization orientation arising from the strong perpendicular magnetocrystalline anisotropy. If the magnetization arranges itself out-of-plane narrow Bloch walls occur. In the present paper, both field and current-driven domain wall motion have been investigated for this system, using micromagnetic simulations. Three types of geometries have been taken into account: bulk, thin film and wire, and for all of them a full comparison is done between the effect of the applied field and injected current. The reduction of the system's dimension induces the decrease of the critical field and the critical current, but it does not influence the domain wall displacement mechanism.

  5. Energy-based ferromagnetic material model with magnetic anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Steentjes, Simon, E-mail: simon.steentjes@iem.rwth-aachen.de [Institute of Electrical Machines - RWTH Aachen University, Schinkelstr. 4, D-52056 Aachen (Germany); Henrotte, François, E-mail: francois.henrotte@uclouvain.be [Institute of Mechanics Materials and Civil Engineering - UCL, Av. G. Lemaître 4-6, B-1348 Louvain-la-Neuve (Belgium); Hameyer, Kay [Institute of Electrical Machines - RWTH Aachen University, Schinkelstr. 4, D-52056 Aachen (Germany)

    2017-03-01

    Non-oriented soft magnetic materials are commonly assumed to be magnetically isotropic. However, due to the rolling process a preferred direction exists along the rolling direction. This uniaxial magnetic anisotropy, and the related magnetostriction effect, are critical to the accurate calculation of iron losses and magnetic forces in rotating electrical machines. This paper proposes an extension of an isotropic energy-based vector hysteresis model to account for these two effects. - Highlights: • Energy-based vector hysteresis model with magnetic anisotropy. • Two-scale model to account for pinning field distribution. • Pinning force and reluctivity are extended to anisotropic case.

  6. Determination of plastic anisotropy of zirconium alloys cladding

    International Nuclear Information System (INIS)

    Yamshchikov, N.V.; Prasolov, P.F.; Shestak, V.E.

    1991-01-01

    Method for determining plastic anisotropy of zurconium alloy cladding is described. It is based on consideration of material as a combination of transversal crystallites with known distribution over orientations. Such approach enables to describe cladding resistance to plastic deformation at arbitrary stressed state, using the results of texture investigations and uniaxial tests of samples, cut out of claddings along three directions. Plastic anisotropy of fuel element claddings 9.15 and 13.6 mm in diameter up to several percents of plastic deformation is shown

  7. Magnetic anisotropies in SmCo thin films

    International Nuclear Information System (INIS)

    Chen, K.

    1993-01-01

    A systemic study of the deposition processes and magnetic properties for the Sm-Co film system has been carried out. Films of Sm-Co system with various magnetic anisotropies have been synthesized through sputter deposition in both crystalline and amorphous phases. The origins of various anisotropies have been studied. Thermalized sputter deposition process control was used to synthesize Fe enriched Sm-Co films with rhombohedral Th 2 Zn 17 type structure. The film exhibited unusually strong textures with the crystallographic c axes of the crystallites aligned in the film plane. A large anisotropy was resulted with easy axis in the film plane. A well defined and large in-the-film-plane anisotropy of exceptionally high value of 3.3 x 10 6 erg/cm 3 has been obtained in the amorphous SmCo films by applying a magnetic field in the film plane during deposition. It was found that the in-the-film-plane anisotropy depended essentially on the applied field and Sm concentration. For films not synthesized through thermallized sputtering, the easy axis of the film could reoriented. A perpendicular anisotropy was also presented in the film synthesized through thermallized sputtering deposition. A large in-plane anisotropy was obtained in films deposited above ambient temperatures. It was concluded that the surface induced short range ordering was the origin of the in-the-film-phase anisotropy observed in amorphous film deposited in the presence of a magnetic field. The formation mechanism was different from that of the short range ordering induced by field annealing. The perpendicular anisotropy was shown to be growth induced. Large in-plane anisotropy in amorphous films was resulted form partial crystallization in the film. Both the formation of growth induced structure and partial crystallization in the film prevented the formation of the pair ordering and decreased in-the-film-plane anisotropy

  8. Effective stress coefficient for uniaxial strain condition

    DEFF Research Database (Denmark)

    Alam, M.M.; Fabricius, I.L.

    2012-01-01

    one dimensional rock mechanical deformation. We further investigated the effect of boundary condition on the stress dependency of effective stress coefficient and discussed its application in reservoir study. As stress field in the reservoirs are most unlikely to be hydrostatic, effective stress...... determined under uniaxial strain condition will be more relevant in reservoir studies. Copyright 2012 ARMA, American Rock Mechanics Association....

  9. Long-wavelength optical phonon behavior in uniaxial strained graphene: Role of electron-phonon interaction

    OpenAIRE

    Assili, Mohamed; Haddad, Sonia

    2014-01-01

    We derive the frequency shifts and the broadening of $\\Gamma$ point longitudinal optical (LO) and transverse optical (TO) phonon modes, due to electron-phonon interaction, in graphene under uniaxial strain as a function of the electron density and the disorder amount. We show that, in the absence of a shear strain component, such interaction gives rise to a lifting of the degeneracy of the LO and TO modes which contributes to the splitting of the G Raman band. The anisotropy of the electronic...

  10. Effects of Transverse Magnetic Anisotropy on Current-Induced Spin Switching

    OpenAIRE

    Misiorny, Maciej; Barnaś, Józef

    2013-01-01

    Spin-polarized transport through bistable magnetic adatoms or single-molecule magnets (SMMs), which exhibit both uniaxial and transverse magnetic anisotropy, is considered theoretically. The main focus is on the impact of transverse anisotropy on transport characteristics and the adatom's/SMM's spin. In particular, we analyze the role of quantum tunneling of magnetization (QTM) in the mechanism of the current-induced spin switching, and show that the QTM phenomenon becomes revealed as resonan...

  11. Uniaxial alignment of triisopropylsilylethynyl pentacene via zone-casting technique.

    Science.gov (United States)

    Su, Yajun; Gao, Xiang; Liu, Jiangang; Xing, Rubo; Han, Yanchun

    2013-09-14

    Uniaxially aligned triisopropylsilylethynyl pentacene (TIPS-pentacene) crystals over a large area were fabricated using zone-casting technique. The array of TIPS-pentacene displayed a high orientation degree with a dichroic ratio (DR) of 0.80. The crystals were arranged with c axis perpendicular to the substrate and the long axis of the ribbon corresponded to the a axis of TIPS-pentacene. The properties of the solutions and the processing parameters were shown to influence the formation of the oriented TIPS-pentacene crystalline array. Solvent with a low boiling point (such as chloroform) favoured the orientation of the ribbon-like crystals. The concentration of the solution should be appropriate, ensuring the crystallization velocity of TIPS-pentacene matching with the receding of the meniscus. Besides, we proved that the casting speed should be large enough to induce a sufficient concentration gradient. The orientation mechanism of TIPS-pentacene was attributed to a synergy of the ordered nuclei and a match between the crystallization velocity and the casting speed. Field effect transistors (FETs) based on the oriented TIPS-pentacene crystalline array showed a mobility of 0.67 cm(2) V(-1) s(-1).

  12. The transition from longitudinal to perpendicular recording

    International Nuclear Information System (INIS)

    Richter, H J

    2007-01-01

    After more than 30 years of research, hard disk drives using perpendicular recording are finally commercially available. This review is a follow-up of a review written in 1999 and addresses the basic physics of perpendicular recording with special emphasis on the read and the write process and the magnetic aspects of the recording media. The paper also surveys various technical difficulties which prevented an earlier implementation of perpendicular recording. The paper closes with a short overview of alternative technologies that allow even higher storage densities. (topical review)

  13. Magnetization measurement of single La{sub 0.67}Ca{sub 0.33}MnO{sub 3} nanotubes in perpendicular magnetic fields using a micromechanical torsional oscillator

    Energy Technology Data Exchange (ETDEWEB)

    Antonio, D., E-mail: dario.antonio@cab.cnea.gov.a [Comision Nacional de Energia Atomica, Centro Atomico Bariloche, (8400) S. C. de Bariloche (Argentina); Dolz, M.I.; Pastoriza, H. [Comision Nacional de Energia Atomica, Centro Atomico Bariloche, (8400) S. C. de Bariloche (Argentina)

    2010-03-15

    Using a silicon micromechanical resonator as a sensitive magnetometer, the authors have studied both experimentally and theoretically the magnetic behavior of two isolated ferromagnetic nanotubes of perovskite La{sub 0.67}Ca{sub 0.33}MnO{sub 3}. The article investigates the specific configuration where a magnetic field H is applied perpendicular to the magnetic easy axis of an isolated nanotube characterized by an uniaxial anisotropy constant K. In this situation, the magnetization M reduces the effective elastic constant k{sub M} of the resonator. This softening of the mechanical system is opposed to the hardening effect of M observed in a previous work, where H was applied parallel to the easy axis. Moreover, in this magnetic field configuration two distinct magnetization regimes are manifested, depending on the magnitude of H. For H>>2K/M the magnetization is almost parallel to the applied magnetic field and for H<<2K/M it is almost parallel to the easy axis of the nanotube. At a certain value of H there is a sharp transition from one regime to the other, accompanied by a peak in the energy dissipation.

  14. Elastic anisotropy of crystals

    Directory of Open Access Journals (Sweden)

    Christopher M. Kube

    2016-09-01

    Full Text Available An anisotropy index seeks to quantify how directionally dependent the properties of a system are. In this article, the focus is on quantifying the elastic anisotropy of crystalline materials. Previous elastic anisotropy indices are reviewed and their shortcomings discussed. A new scalar log-Euclidean anisotropy measure AL is proposed, which overcomes these deficiencies. It is based on a distance measure in a log-Euclidean space applied to fourth-rank elastic tensors. AL is an absolute measure of anisotropy where the limiting case of perfect isotropy yields zero. It is a universal measure of anisotropy applicable to all crystalline materials. Specific examples of strong anisotropy are highlighted. A supplementary material provides an anisotropy table giving the values of AL for 2,176 crystallite compounds.

  15. Size dependence of spin-torque induced magnetic switching in CoFeB-based perpendicular magnetization tunnel junctions (invited)

    Science.gov (United States)

    Sun, J. Z.; Trouilloud, P. L.; Gajek, M. J.; Nowak, J.; Robertazzi, R. P.; Hu, G.; Abraham, D. W.; Gaidis, M. C.; Brown, S. L.; O'Sullivan, E. J.; Gallagher, W. J.; Worledge, D. C.

    2012-04-01

    CoFeB-based magnetic tunnel junctions with perpendicular magnetic anisotropy are used as a model system for studies of size dependence in spin-torque-induced magnetic switching. For integrated solid-state memory applications, it is important to understand the magnetic and electrical characteristics of these magnetic tunnel junctions as they scale with tunnel junction size. Size-dependent magnetic anisotropy energy, switching voltage, apparent damping, and anisotropy field are systematically compared for devices with different materials and fabrication treatments. Results reveal the presence of sub-volume thermal fluctuation and reversal, with a characteristic length-scale of the order of approximately 40 nm, depending on the strength of the perpendicular magnetic anisotropy and exchange stiffness. To have the best spin-torque switching efficiency and best stability against thermal activation, it is desirable to optimize the perpendicular anisotropy strength with the junction size for intended use. It also is important to ensure strong exchange-stiffness across the magnetic thin film. These combine to give an exchange length that is comparable or larger than the lateral device size for efficient spin-torque switching.

  16. Oriented Morphology and Anisotropic Transport in Uniaxially Stretched Perfluorosulfonate Ionomer Membranes

    Energy Technology Data Exchange (ETDEWEB)

    J Park; J Li; G Divoux; L Madsen; R Moore

    2011-12-31

    Relations between morphology and transport sensitively govern proton conductivity in perfluorsulfonate ionomers (PFSIs) and thus determine useful properties of these technologically important materials. In order to understand such relations, we have conducted a broad systematic study of H{sup +}-form PFSI membranes over a range of uniaxial extensions and water uptakes. On the basis of small-angle X-ray scattering (SAXS) and {sup 2}H NMR spectroscopy, uniaxial deformation induces a strong alignment of ionic domains along the stretching direction. We correlate ionic domain orientation to transport using pulsed-field-gradient {sup 1}H NMR measurements of water diffusion coefficients along the three orthogonal membrane directions. Intriguingly, we observe that uniaxial deformation enhances water transport in one direction (parallel-to-draw direction) while reducing it in the other two directions (two orthogonal directions relative to the stretching direction). We evaluate another important transport parameter, proton conductivity, along two orthogonal in-plane directions. In agreement with water diffusion experiments, orientation of ionic channels increases proton conduction along the stretching direction while decreasing it in the perpendicular direction. These findings provide valuable fodder for optimal application of PFSI membranes as well as for the design of next generation polymer electrolyte membranes.

  17. Dependence of magnetic anisotropy on MgO sputtering pressure in Co20Fe60B20/MgO stacks

    Science.gov (United States)

    Kaidatzis, A.; Serletis, C.; Niarchos, D.

    2017-10-01

    We investigated the dependence of magnetic anisotropy of Ta/Co20Fe60B20/MgO stacks on the Ar partial pressure during MgO deposition, in the range between 0.5 and 15 mTorr. The stacks are studied before and after annealing at 300°C and it is shown that magnetic anisotropy significantly depends on Ar partial pressure. High pressure results in stacks with very low perpendicular magnetic anisotropy even after annealing, while low pressure results in stacks with perpendicular anisotropy even at the as-deposited state. A monotonic increase of magnetic anisotropy energy is observed as Ar partial pressure is decreased.

  18. Uniaxial Elongational viscosity of bidisperse polystyrene melts

    DEFF Research Database (Denmark)

    Nielsen, Jens Kromann; Rasmussen, Henrik K.; Hassager, Ole

    2006-01-01

    The startup and steady uniaxial elongational viscosity have been measured for three bidisperse polystyrene (PS) melts, consisting of blends of monodisperse PS with molecular weights of 52 kg/mole or 103 kg/mole and 390 kg/mole. The bidisperse melts have a maximum in the steady elongational...... viscosity, of up to a factor of 7 times the Trouton limit of 3 times the zero-shear viscosity....

  19. Controlling the induced anisotropy in soft magnetic films for high-frequency applications

    NARCIS (Netherlands)

    Chezan, A.R.; Craus, C.B.; Chechenin, N.G.; Vystavel, T.; Hosson, J.Th.M. De; Niesen, L.; Boerma, D.O.

    Nanocrystalline soft magnetic Fe–Zr–N films were successfully deposited by dc magnetron reactive sputtering. The nitrogen content was controlled by varying the Ar/N2 ratio and/or the substrate temperature. The films have saturation magnetization and induced uniaxial anisotropy values in the range

  20. Anisotropic Material Behavior of Uni-axially Compacted Graphite Matrix for HTGR Fuel Compact Fabrication

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Young-Woo; Yeo, Seunghwan; Yoon, Ji-Hae; Cho, Moon Sung [KAERI, Daejeon (Korea, Republic of)

    2016-05-15

    In developing the fuel compact fabrication technology, and fuel graphite material to meet the required material properties, it is essential to investigate the relationship among the process parameters of the matrix graphite powder preparation, the fabrication parameters of fuel element green compact and the heat treatments conditions and the material properties of fuel element. It was observed, during this development, that the pressing technique employed for the compaction fabrication prior to the two successive heat treatments (carbonization and final high temperature heat treatment) was of extreme importance in determining the material properties of the final compact product. In this work, the material behavior of the uni-axially pressed graphite matrix during the carbonization and final heat treatment are evaluated and summarized along the different directions, viz., perpendicular and parallel directions to pressing direction. In this work, the dimensional variations and variations in thermal expansion, thermal conductivity and Vickers hardness of the graphite matrix compact samples in the axial and radial directions prepared by uni-axial pressing are evaluated, and compared with those of samples prepared by cold isostatic pressing with the available data. From this work, the followings are observed. 1) Dimensional changes of matrix graphite green compacts during carbonization show that the difference in radial and axial variations shows a large anisotropic behavior in shrinkage. The radial variation is very small while the axial variation is large. During carbonization, the stresses caused by the force would be released in to the axial direction together with the phenolic resin vapor. 2) Dimensional variation of compact samples in perpendicular and parallel directions during carbonization shows a large difference in behavior when compact sample is prepared by uni-axial pressing. However, when compact sample is prepared by cold isostatic pressing, there is

  1. Anisotropic Material Behavior of Uni-axially Compacted Graphite Matrix for HTGR Fuel Compact Fabrication

    International Nuclear Information System (INIS)

    Lee, Young-Woo; Yeo, Seunghwan; Yoon, Ji-Hae; Cho, Moon Sung

    2016-01-01

    In developing the fuel compact fabrication technology, and fuel graphite material to meet the required material properties, it is essential to investigate the relationship among the process parameters of the matrix graphite powder preparation, the fabrication parameters of fuel element green compact and the heat treatments conditions and the material properties of fuel element. It was observed, during this development, that the pressing technique employed for the compaction fabrication prior to the two successive heat treatments (carbonization and final high temperature heat treatment) was of extreme importance in determining the material properties of the final compact product. In this work, the material behavior of the uni-axially pressed graphite matrix during the carbonization and final heat treatment are evaluated and summarized along the different directions, viz., perpendicular and parallel directions to pressing direction. In this work, the dimensional variations and variations in thermal expansion, thermal conductivity and Vickers hardness of the graphite matrix compact samples in the axial and radial directions prepared by uni-axial pressing are evaluated, and compared with those of samples prepared by cold isostatic pressing with the available data. From this work, the followings are observed. 1) Dimensional changes of matrix graphite green compacts during carbonization show that the difference in radial and axial variations shows a large anisotropic behavior in shrinkage. The radial variation is very small while the axial variation is large. During carbonization, the stresses caused by the force would be released in to the axial direction together with the phenolic resin vapor. 2) Dimensional variation of compact samples in perpendicular and parallel directions during carbonization shows a large difference in behavior when compact sample is prepared by uni-axial pressing. However, when compact sample is prepared by cold isostatic pressing, there is

  2. Capping layer-tailored interface magnetic anisotropy in ultrathin Co{sub 2}FeAl films

    Energy Technology Data Exchange (ETDEWEB)

    Belmeguenai, M., E-mail: belmeguenai.mohamed@univ-paris13.fr; Zighem, F.; Chérif, S. M. [LSPM (CNRS-UPR 3407), Université Paris 13, Sorbonne Paris Cité, 99 Avenue Jean-Baptiste Clément, 93430 Villetaneuse (France); Gabor, M. S., E-mail: mihai.gabor@phys.utcluj.ro; Petrisor, T. [Center for Superconductivity, Spintronics and Surface Science, Department of Physics and Chemistry, Technical University of Cluj-Napoca, Str. Memorandumului No. 28, RO-400114 Cluj-Napoca (Romania); Tiusan, C. [Center for Superconductivity, Spintronics and Surface Science, Department of Physics and Chemistry, Technical University of Cluj-Napoca, Str. Memorandumului No. 28, RO-400114 Cluj-Napoca (Romania); Institut Jean Lamour, CNRS, Lorraine Université, BP 70239, F-54506 Vandoeuvre (France)

    2015-01-14

    Co{sub 2}FeAl (CFA) thin films of various thicknesses (2 nm ≤ d ≤ 50 nm) have been grown on (001) MgO single crystal substrates and then capped with Cr, V, and Ta. Their magnetic and structural properties have been studied by x-ray diffraction (XRD), vibrating sample magnetometry, and broadband microstrip ferromagnetic resonance (MS-FMR). The XRD revealed that the films are epitaxial with the cubic [001] CFA axis normal to the substrate plane and that the chemical order varies from the B2 phase to the A2 phase when decreasing the thickness. The deduced lattice parameters showed that the Cr-capped films exhibit a larger tetragonal distortion, as compared with the films capped with V or Ta. The presence of magnetic dead layers has been observed in CFA samples capped with V and Ta but not in the case of the Cr-capped ones. The effective magnetization, deduced from the fit of MS-FMR measurements, increases (decreases) linearly with the CFA inverse thickness (1/d) for the Cr-capped (Ta-capped) films while it is constant for the V-capped ones. This allows quantifying the perpendicular surface anisotropy coefficients of −0.46 erg/cm{sup 2} and 0.74 erg/cm{sup 2} for Cr and Ta-capped films, respectively. Moreover, the fourfold and the uniaxial anisotropy fields, measured in these films, showed different trends with a respect to the CFA inverse thickness. This allows inferring that a non-negligible part of the fourfold magnetocrystalline term is of interfacial origin.

  3. Perpendicular recording: the promise and the problems

    International Nuclear Information System (INIS)

    Wood, Roger; Sonobe, Yoshiaki; Jin Zhen; Wilson, Bruce

    2001-01-01

    Perpendicular recording has long been advocated as a means of achieving the highest areal densities. In particular, in the context of the 'superparamagnetic limit', perpendicular recording with a soft underlayer promises several key advantages. These advantages include a higher coercivity, thicker media that should permit smaller diameter grains and higher signal-to-noise ratio. Also, the sharper edge-writing will facilitate recording at very high track densities (lower bit aspect ratio). Recent demonstrations of the technology have shown densities comparable with the highest densities reported for longitudinal recording. This paper further examines the promise that perpendicular recording will deliver an increase in areal density two to eight times higher than that achievable with longitudinal recording. There are a number of outstanding issues but the key challenge is to create a low-noise medium with a coercivity that is high and is much larger than the remanent magnetization

  4. Understanding the magnetic anisotropy in Fe-Si amorphous alloys

    Energy Technology Data Exchange (ETDEWEB)

    Diaz, J.; Hamdan, N.M.; Jalil, P.; Hussain, Z.; Valvidares, S.M.; Alameda, J.M.

    2002-08-01

    The origin of the magnetic anisotropy in a very disordered Fe-Si alloy has been investigated. The alloy containing 40 percent at. Si was prepared in the form of a thin film in a DC magnetron sputtering chamber. Structural disorder was obtained from Extended X-ray Absorption Fine Structure spectroscopy. The uniformity and lack of inhomogeneities at a microscopic level was checked by measuring their transverse magnetic susceptibility and hysteresis loops. The orbital component of the magnetic moment was measured by X-ray Magnetic Circular Dichroism spectroscopy. The orbital moment was extraordinary high, 0.4mB. Such a high value contrasted with the relatively small uniaxial anisotropy energy of the thin film (2kJ/m3). This suggests that the cause of the magnetic anisotropy in this alloy was a small degree of correlation in the orientation of the local orbital moments along a preferential direction.

  5. Understanding the magnetic anisotropy in Fe-Si amorphous alloys

    International Nuclear Information System (INIS)

    Diaz, J.; Hamdan, N.M.; Jalil, P.; Hussain, Z.; Valvidares, S.M.; Alameda, J.M.

    2002-01-01

    The origin of the magnetic anisotropy in a very disordered Fe-Si alloy has been investigated. The alloy containing 40 percent at. Si was prepared in the form of a thin film in a DC magnetron sputtering chamber. Structural disorder was obtained from Extended X-ray Absorption Fine Structure spectroscopy. The uniformity and lack of inhomogeneities at a microscopic level was checked by measuring their transverse magnetic susceptibility and hysteresis loops. The orbital component of the magnetic moment was measured by X-ray Magnetic Circular Dichroism spectroscopy. The orbital moment was extraordinary high, 0.4mB. Such a high value contrasted with the relatively small uniaxial anisotropy energy of the thin film (2kJ/m3). This suggests that the cause of the magnetic anisotropy in this alloy was a small degree of correlation in the orientation of the local orbital moments along a preferential direction

  6. Anisotropy effect on strengths of metamorphic rocks

    Directory of Open Access Journals (Sweden)

    Ahmet Özbek

    2018-02-01

    Full Text Available This paper aims to study the effect of anisotropy on strengths of several metamorphic rocks of southern (Çine submassif of Menderes metamorphic massif in southwest Turkey. Four different metamorphic rocks including foliated phyllite, schist, gneiss and marble (calcschist were selected and examined. Discontinuity surveys were made along lines for each rock and evaluated with DIPS program. L-type Schmidt hammer was applied in the directions parallel and perpendicular to foliation during the field study. Several hand samples and rock blocks were collected during the field study for measurements of dry and saturated densities, dry and saturated unit weights and porosity, and for petrographic analysis and strength determination in laboratory. L- and N-type Schmidt hammers were applied in the directions perpendicular (anisotropy angle of 0° and parallel (anisotropy angle of 90° to the foliation on selected blocks of phyllite, schist, gneiss and marble (calcschist. The phyllite and schist have higher porosity and lower density values than the other rocks. However, coarse crystalline gneiss and marble (calcschist have higher rebound values and strengths, and they are classified as strong–very strong rocks. Generally, the rebound values in the direction perpendicular to the foliation are slightly higher than that in the direction parallel to foliation. Rebound values of N-type Schmidt hammer are higher than the L-type values except for phyllite. Sometimes, the rebound values of laboratory and field applications gave different results. This may result from variable local conditions such as minerals differentiation, discontinuities, water content, weathering degree and thickness of foliated structure.

  7. Giant enhancement of magnetocrystalline anisotropy in ultrathin manganite films via nanoscale 1D periodic depth modulation

    Science.gov (United States)

    Rajapitamahuni, Anil; Zhang, Le; Singh, Vijay; Burton, John; Koten, Mak; Shield, Jeffrey; Tsymbal, Evgeny; Hong, Xia

    We report a unusual giant enhancement of in-plane magnetocrystalline anisotropy (MCA) in ultrathin colossal magnetoresistive oxide films due to 1D nanoscale periodic depth modulation. High quality epitaxial thin films of La0.67Sr0.33MnO3 (LSMO) of thickness 6 nm were grown on (001) SrTiO3 substrates via off-axis radio frequency magnetron sputtering. The top 2 nm of LSMO films are patterned into periodic nano-stripes using e-beam lithography and reactive ion etching. The resulting structure consists of nano-stripes of 2 nm height and 100-200 nm width on top of a 4 nm thick continuous base layer. We employed planar Hall effect measurements to study the in-plane magnetic anisotropy of the unpatterned and nanopatterned films. The unpatterned films show a biaxial anisotropy with easy axis along [110]. The extracted anisotropy energy density is ~1.1 x 105 erg/cm3, comparable to previously reported values. In the nanopatterned films, a strong uniaxial anisotropy is developed along one of the biaxial easy axes. The corresponding anisotropy energy density is ~5.6 x 106 erg/cm3 within the nano-striped volume, comparable to that of Co. We attribute the observed uniaxial MCA to MnO6 octahedral rotations/tilts and the enhancement in the anisotropy energy density to the strain gradient within the nano-stripes.

  8. Uniaxial compression test series on Bullfrog Tuff

    International Nuclear Information System (INIS)

    Price, R.H.; Jones, A.K.; Nimick, K.G.

    1982-04-01

    Nineteen uniaxial compressive experiments were performed on samples of the Bullfrog Member of the Crater Flat Tuff, obtained from drillhole USW-G1 at Yucca Mountain on the Nevada Test Site. The water saturated samples were deformed at a nominal strain rate of 10 -5 sec -1 , atmospheric pressure and room temperature. Resultant unconfined compressive strengths, axial strains to failure, Young's moduli and Poisson's ratios ranged from 4.63 to 153. MPa, .0028 to .0058, 2.03 to 28.9 GPa and .08 to .16, respectively

  9. Comparison between uniaxially and isostatically compacted bentonite

    International Nuclear Information System (INIS)

    Kalbantner, P.; Sjoeblom, R.; Boergesson, Lennart

    2001-12-01

    The purpose of the present report is to provide the Swedish Nuclear Fuel and Waste Management Company (SKB) with the knowledge base needed for their selection of reference method for manufacturing of bentonite blocks. The purpose is also to provide support for the direction of the further development work. Three types of blocks are compared in the present report: uniaxially compacted medium high blocks, isostatically compacted medium high blocks, isostatically compacted high blocks. The analyses is based on three process systems relating to the sequence of excavation of bentonite-transport-powder preparation-compaction-handling and emplacement of bentonite blocks. The need for further knowledge has been identified and documented in conjunction with these analyses. The comparison is primarily made with regard to the criteria safety/risk, quality/ technique and economy. It is carried out through identification of issues of significance and subsequent analysis and evaluation as well as more formally in a simplified AHP (AHP = Analytical Hierarchic Process). The result of the analyses is that the isostatic technique is applicable for the production of high as well as medium size blocks. The pressed blocks are assessed to fulfil the basic requirements with a very large margin. The result of the analyses is also that the uniaxial technique is applicable for the preparation of medium size blocks, which are assessed to fulfil the basic requirements with a large margin. The need for development and process control is assessed to be somewhat higher for the uniaxial technique. One example is the friction against the walls of the die during the compaction, including the significance of this friction for the development of stresses and discontinuities in the block. These results support a selection of the isostatic technique as the reference technique as it provides flexibility in the choice of block height. The uniaxial technique can form a second alternative if medium high

  10. Uniaxial and Multiaxial Creep Testing of Copper

    International Nuclear Information System (INIS)

    Auerkari, Pertti; Holmstroem, Stefan; Veivo, Juha; Salonen, Jorma; Nenonen, Pertti; Laukkanen, Anssi

    2003-12-01

    Multiaxial (compact tension, CT) creep testing has been performed for copper with 79 ppm phosphorus and 60 ppm oxygen. The test load levels were selected according to results from preceding uniaxial creep testing and FE analysis of the CT specimens. Interrupted testing was used for metallographic inspection of the specimens for creep damage. After 7,900 h and 10,300 h of testing at 150 deg C and 46 MPa (reference stress), inspected CT specimens showed cavity indications with a low maximum density ( 2 ) and a typical maximum dimension of less than about 1 μm near the notch tip. From previous experience on creep cavitation damage, the expected minimum life to crack initiation at the notch tip would be at least 40,000 hours, but could be considerably longer because the cavity indications are suspected to originate at least partly from precipitates in specimen preparation. The interrupted testing of CT specimens also showed a 'segregation zone' along some grain boundaries, mainly near the notch tip. This zone appears to contain more P and O than the surrounding matrix, but less than the narrow grain boundary films that are already present in the as-new material. The zone is readily etched and shows a relatively sharp edge towards the matrix without an obvious phase boundary. Using converted multiaxial (CT) testing results, the predicted isothermal uniaxial creep life at 150 deg C/46 MPa is about 1,900 years. The corresponding creep life directly predicted from uniaxial data is 3,100 years, when estimated from a parametric best fit expression according to PD6605. Although the two results are satisfactorily within a factor of two in time, the uncertainties in the extended extrapolations remain large. Further testing is recommended, with at least two creep enhancing factors present. Such testing could include notched creep testing at 120-180 deg C in a corrosive environment, and notched model vessel creep testing at elevated pressure. It is also recommended that longer

  11. Strongly coupled modes of M and H for perpendicular resonance

    Science.gov (United States)

    Sun, Chen; Saslow, Wayne M.

    2018-05-01

    We apply the equations for the magnetization M ⃗ and field H ⃗ to study their coupled modes for a semi-infinite ferromagnet, conductor, or insulator with magnetization M0 and field H0 normal to the plane (perpendicular resonance) and wave vector normal to the plane, which makes the modes doubly degenerate. With dimensionless damping constant α and dimensionless transverse susceptibility χ⊥=M0/He(He≡H0-M0) , we derive an analytic expression for the wave vector squared, showing that M ⃗ and H ⃗ are nearly decoupled only if α ≫χ⊥ . This is violated in the ferromagnetic regime, although a first correction is found to give good agreement away from resonance. Emphasizing the conductor permalloy as a function of H0 we study the eigenvalues and eigenmodes and the dissipation rate due to absorption both from the total effective field and from the Joule heating. (We include the contribution of the nonuniform exchange energy term, needed for energy conservation.) Using these modes we then apply, for a semi-infinite ferromagnet, a range of boundary conditions (i.e., surface anisotropies) on M⊥ to find the reflection coefficient R and the reflectivity |R| 2. As a function of H0, absorption is dominated by the the skin depth mode (primarily H ⃗) except near the resonance and at a higher-field Hd associated with a dip in the reflectivity, whose position above the main resonance varies quadratically with the surface anisotropy Ks. The dip is driven by the boundary condition on M ⃗; the coefficient of the (primarily) M ⃗ mode becomes very small at the dip, being compensated by an increase in the amplitude of the M ⃗ mode, which has a Lorentzian line shape of height ˜α-1 and width ˜α .

  12. Shape anisotropy: tensor distance to anisotropy measure

    Science.gov (United States)

    Weldeselassie, Yonas T.; El-Hilo, Saba; Atkins, M. S.

    2011-03-01

    Fractional anisotropy, defined as the distance of a diffusion tensor from its closest isotropic tensor, has been extensively studied as quantitative anisotropy measure for diffusion tensor magnetic resonance images (DT-MRI). It has been used to reveal the white matter profile of brain images, as guiding feature for seeding and stopping in fiber tractography and for the diagnosis and assessment of degenerative brain diseases. Despite its extensive use in DT-MRI community, however, not much attention has been given to the mathematical correctness of its derivation from diffusion tensors which is achieved using Euclidean dot product in 9D space. But, recent progress in DT-MRI has shown that the space of diffusion tensors does not form a Euclidean vector space and thus Euclidean dot product is not appropriate for tensors. In this paper, we propose a novel and robust rotationally invariant diffusion anisotropy measure derived using the recently proposed Log-Euclidean and J-divergence tensor distance measures. An interesting finding of our work is that given a diffusion tensor, its closest isotropic tensor is different for different tensor distance metrics used. We demonstrate qualitatively that our new anisotropy measure reveals superior white matter profile of DT-MR brain images and analytically show that it has a higher signal to noise ratio than fractional anisotropy.

  13. Ion-beam texturing of uniaxially textured Ni films

    International Nuclear Information System (INIS)

    Park, S.J.; Norton, D.P.; Selvamanickam, Venkat

    2005-01-01

    The formation of biaxial texture in uniaxially textured Ni thin films via Ar-ion irradiation is reported. The ion-beam irradiation was not simultaneous with deposition. Instead, the ion beam irradiates the uniaxially textured film surface with no impinging deposition flux, which differs from conventional ion-beam-assisted deposition. The uniaxial texture is established via a nonion beam process, with the in-plane texture imposed on the uniaxial film via ion beam bombardment. Within this sequential ion beam texturing method, grain alignment is driven by selective etching and grain overgrowth

  14. Superconductivity under uniaxial compression in β-(BDA-TTP) salts

    International Nuclear Information System (INIS)

    Suzuki, T.; Onari, S.; Ito, H.; Tanaka, Y.

    2009-01-01

    In order to clarify the mechanism of organic superconductor β-(BDA-TTP) salts. We study the superconductivity under uniaxial compression with non-dimerized two-band Hubbard model. We have calculated the uniaxial compression dependence of T c by solving the Eliashberg's equation using the fluctuation exchange (FLEX) approximation. The transfer integral under the uniaxial compression was estimated by the extended Huckel method. We have found that non-monotonic behaviors of T c in experimental results under uniaxial compression are understood taking the spin frustration and spin fluctuation into account.

  15. Superconductivity under uniaxial compression in β-(BDA-TTP) salts

    Science.gov (United States)

    Suzuki, T.; Onari, S.; Ito, H.; Tanaka, Y.

    2009-10-01

    In order to clarify the mechanism of organic superconductor β-(BDA-TTP) salts. We study the superconductivity under uniaxial compression with non-dimerized two-band Hubbard model. We have calculated the uniaxial compression dependence of T c by solving the Eliashberg’s equation using the fluctuation exchange (FLEX) approximation. The transfer integral under the uniaxial compression was estimated by the extended Huckel method. We have found that non-monotonic behaviors of T c in experimental results under uniaxial compression are understood taking the spin frustration and spin fluctuation into account.

  16. Superconductivity under uniaxial compression in beta-(BDA-TTP) salts

    Energy Technology Data Exchange (ETDEWEB)

    Suzuki, T., E-mail: suzuki@rover.nuap.nagoya-u.ac.j [Department of Applied Physics and JST, TRIP, Nagoya University, Chikusa, Nagoya 464-8603 (Japan); Onari, S.; Ito, H.; Tanaka, Y. [Department of Applied Physics and JST, TRIP, Nagoya University, Chikusa, Nagoya 464-8603 (Japan)

    2009-10-15

    In order to clarify the mechanism of organic superconductor beta-(BDA-TTP) salts. We study the superconductivity under uniaxial compression with non-dimerized two-band Hubbard model. We have calculated the uniaxial compression dependence of T{sub c} by solving the Eliashberg's equation using the fluctuation exchange (FLEX) approximation. The transfer integral under the uniaxial compression was estimated by the extended Huckel method. We have found that non-monotonic behaviors of T{sub c} in experimental results under uniaxial compression are understood taking the spin frustration and spin fluctuation into account.

  17. Temperature dependence of magnetic anisotropies in ultrathin Fe film on vicinal Si(111)

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Yong-Sheng; He, Wei; Ye, Jun; Hu, Bo; Tang, Jin; Zhang, Xiang-Qun [State Key Laboratory of Magnetism and Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Cheng, Zhao-Hua, E-mail: zhcheng@aphy.iphy.ac.cn [State Key Laboratory of Magnetism and Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190 (China)

    2017-05-01

    The temperature dependence of magnetic anisotropy of ultrathin Fe film with different thickness epitaxially grown on vicinal Si(111) substrate has been quantitatively investigated using the anisotropic magnetoresistance(AMR) measurements. Due to the effect of the vicinal substrate, the magnetic anisotropy is the superposition of a four-fold, a two-fold and a weakly six-fold contribution. It is found that the temperature dependence of the first-order magnetocrystalline anisotropies coefficient follows power laws of the reduced magnetization m(T)(=M(T)/M(0)) being consistent with the Callen and Callen's theory. However the temperature dependence of uniaxial magnetic anisotropy (UMA) shows novel behavior that decreases roughly as a function of temperature with different power law for samples with different thickness. We also found that the six-fold magnetocrystalline anisotropy is almost invariable over a wide temperature range. Possible mechanisms leading to the different exponents are discussed.

  18. Nanoscale magnetic ratchets based on shape anisotropy

    Science.gov (United States)

    Cui, Jizhai; Keller, Scott M.; Liang, Cheng-Yen; Carman, Gregory P.; Lynch, Christopher S.

    2017-02-01

    Controlling magnetization using piezoelectric strain through the magnetoelectric effect offers several orders of magnitude reduction in energy consumption for spintronic applications. However strain is a uniaxial effect and, unlike directional magnetic field or spin-polarized current, cannot induce a full 180° reorientation of the magnetization vector when acting alone. We have engineered novel ‘peanut’ and ‘cat-eye’ shaped nanomagnets on piezoelectric substrates that undergo repeated deterministic 180° magnetization rotations in response to individual electric-field-induced strain pulses by breaking the uniaxial symmetry using shape anisotropy. This behavior can be likened to a magnetic ratchet, advancing magnetization clockwise with each piezostrain trigger. The results were validated using micromagnetics implemented in a multiphysics finite elements code to simulate the engineered spatial and temporal magnetic behavior. The engineering principles start from a target device function and proceed to the identification of shapes that produce the desired function. This approach opens a broad design space for next generation magnetoelectric spintronic devices.

  19. Mechanism of tailored magnetic anisotropy in amorphous Co{sub 68}Fe{sub 24}Zr{sub 8} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Fu, Yu, E-mail: yu.fu@uni-due.de, E-mail: cangcangzhulin@gmail.com; Meckenstock, R.; Farle, M. [Fakultät für Physik and Center for Nanointegration Duisburg-Essen (CeNIDE), Universität Duisburg-Essen, 47057 Duisburg (Germany); Barsukov, I., E-mail: ibarsuko@uci.edu [Fakultät für Physik and Center for Nanointegration Duisburg-Essen (CeNIDE), Universität Duisburg-Essen, 47057 Duisburg (Germany); Physics and Astronomy, University of California, Irvine, California 92697 (United States); Lindner, J. [Fakultät für Physik and Center for Nanointegration Duisburg-Essen (CeNIDE), Universität Duisburg-Essen, 47057 Duisburg (Germany); Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf e.V., Bautzner Landstr. 400, 01328 Dresden (Germany); Raanaei, H. [Department of Physics, Persian Gulf University, Bushehr 75169 (Iran, Islamic Republic of); Hjörvarsson, B. [Department of Physics and Astronomy, Uppsala University, Box 516 SE-75120 Uppsala (Sweden)

    2014-02-17

    The mechanism of tailored magnetic anisotropy in amorphous Co{sub 68}Fe{sub 24}Zr{sub 8} thin films was investigated by ferromagnetic resonance (FMR) on samples deposited without an applied magnetic field, with an out-of-plane field and an in-plane field. Analysis of FMR spectra profiles, high frequency susceptibility calculations, and statistical simulations using a distribution of local uniaxial magnetic anisotropy reveal the presence of atomic configurations with local uniaxial anisotropy, of which the direction can be tailored while the magnitude remains at an intrinsically constant value of 3.0(2) kJ/m{sup 3}. The in-plane growth field remarkably sharpens the anisotropy distribution and increases the sample homogeneity. The results benefit designing multilayer spintronic devices based on highly homogeneous amorphous layers with tailored magnetic anisotropy.

  20. Diffraction Plane Dependence of Micro Residual Stresses in Uniaxially Extended Carbon Steels

    Directory of Open Access Journals (Sweden)

    T. Hanabusa

    2010-12-01

    Full Text Available In the stress measurement using X-ray or neutron diffraction, an elastic anisotropy as well as a plastic anisotropy of crystal must be carefully considered. In the X-ray and neutron diffraction stress measurement for polycrystalline materials, a particular {hkl} plane is used in measuring lattice strains. The dependence of an X-ray elastic constant on a diffraction plane is a typical example caused by an elastic anisotropy of the crystal. The yield strength and the work hardening rate of a single crystal depend on a crystallographic direction of the crystal. The difference in the yield strength and the work hardening rate relating to the crystallographic direction develops different residual stresses measured on each {hkl} diffraction after plastic deformation of a polycrystalline material. The present paper describes the result of the neutron stress measurement on uniaxially extended low and middle carbon steels. A tri-axial residual stress state developed in the extended specimens was measured on different kind of {hkl} diffraction plane. The measurement on the {110}, {200} and {211} diffraction showed that residual stresses increased with increasing the plastic elongation and the residual stresses on {110} were compressive, {200} were tensile and those on {211} were the middle of the former two planes.

  1. Magnetic anisotropy of ultrafine 316L stainless steel fibers

    Energy Technology Data Exchange (ETDEWEB)

    Shyr, Tien-Wei, E-mail: twshyr@fcu.edu.tw [Department of Fiber and Composite Materials, Feng Chia University, No. 100, Wenhwa Road, Seatwen, Taichung 40724, Taiwan, ROC (China); Huang, Shih-Ju [Department of Fiber and Composite Materials, Feng Chia University, No. 100, Wenhwa Road, Seatwen, Taichung 40724, Taiwan, ROC (China); Wur, Ching-Shuei [Department of Physics, National Cheng Kung University, No. 1, University Road, Tainan 70101, Taiwan, ROC (China)

    2016-12-01

    An as-received 316L stainless steel fiber with a diameter of 20 μm was drawn using a bundle drawing process at room temperature to form ultrafine stainless steel fibers with diameters of 12, 8, and 6 μm. The crystalline phases of the fibers were analyzed using the X-ray diffraction (XRD) profile fitting technique. The grain sizes of γ-austenite and α′-martensite were reduced to nanoscale sizes after the drawing process. XRD analysis and focused ion beam-scanning electron microscope observations showed that the newly formed α′-martensitic grains were closely arrayed in the drawing direction. The magnetic property was measured using a superconducting quantum interference device vibrating sample magnetometer. The magnetic anisotropy of the fibers was observed by applying a magnetic field parallel and perpendicular to the fiber axis. The results showed that the microstructure anisotropy including the shape anisotropy, magnetocrystalline anisotropy, and the orientation of the crystalline phases strongly contributed to the magnetic anisotropy. - Highlights: • The martensitic transformation of the 316L SS fiber occurred during the cold drawn. • The grain sizes of γ-austenite and α′-martensite were reduced to the nanoscale. • The newly formed martensitic grains were closely arrayed in the drawing direction. • The drawing process caused the magnetic easy axis to be aligned with the fiber axis. • The microstructure anisotropy strongly contributed to the magnetic anisotropy.

  2. Electronic, magnetic, and magnetocrystalline anisotropy properties of light lanthanides

    Science.gov (United States)

    Hackett, Timothy A.; Baldwin, D. J.; Paudyal, D.

    2017-11-01

    Theoretical understanding of interactions between localized and mobile electrons and the crystal environment in light lanthanides is important because of their key role in much needed magnetic anisotropy in permanent magnet materials that have a great impact in automobile and wind turbine applications. We report electronic, magnetic, and magnetocrystalline properties of these basic light lanthanide elements studied from advanced density functional theory (DFT) calculations. We find that the inclusion of onsite 4f electron correlation and spin orbit coupling within the full-potential band structure is needed to understand the unique magnetocrystalline properties of these light lanthanides. The onsite electron correlation, spin orbit coupling, and full potential for the asphericity of charge densities must be taken into account for the proper treatment of 4f states. We find the variation of total energy as a function of lattice constants that indicate multiple structural phases in Ce contrasting to a single stable structure obtained in other light lanthanides. The 4f orbital magnetic moments are partially quenched as a result of crystalline electric field splitting that leads to magnetocrystalline anisotropy. The charge density plots have similar asphericity and environment in Pr and Nd indicating similar magnetic anisotropy. However, Ce and Sm show completely different asphericity and environment as both orbital moments are significantly quenched. In addition, the Fermi surface structures exemplified in Nd indicate structural stability and unravel a cause of anisotropy. The calculated magnetocrystalline anisotropy energy (MAE) reveals competing c-axis and in-plane anisotropies, and also predicts possibilities of unusual structural deformations in light lanthanides. The uniaxial magnetic anisotropy is obtained in the double hexagonal closed pack structures of the most of the light lanthanides, however, the anisotropy is reduced or turned to planar in the low symmetry

  3. Thermal fluctuations in perpendicular recording media: New methodology for estimation of activation moment

    International Nuclear Information System (INIS)

    Mamiya, H; Oba, Y; Ohnuma, M; Hagiya, H; Oku, T; Suzuki, J; Yokoyama, M; Nishihara, Y; Katayama, T; Awano, H; Koda, T

    2011-01-01

    In nanoparticulate films with perpendicular magnetic anisotropy, a large demagnetizing field almost compensates for the experimentally designed change in the magnetic field applied parallel to the film normal. We propose a new method based on field-cycling to eliminate the uncertainty in the demagnetizing response from the analysis of the activation volume of the reversal or magnetic activation moment in such films. In this method, the applied field induced variation in the magnetic relaxation rate is measured before the effect of the demagnetizing field becomes dominant. We also discuss an analogical thermal-cycling method to clarify the temperature dependence of the barrier height for magnetization reversal in a magnetic field. We apply these methods to a Co 74 Pt 16 Cr 10 -SiO 2 nanoparticulate film as an example. The results demonstrate that these methods are useful for studying thermal fluctuations in perpendicular recording media.

  4. The sandwich domain structure in a Fe-based amorphous ribbon with uniaxial magnetic anisotropy

    International Nuclear Information System (INIS)

    Zhmetko, D.N.; Matsura, A.V.; Troschenkov, Y.N.; Seidametov, S.V.

    2011-01-01

    The formation and motion of two domain walls parallel to the ribbon surface are discovered during its dynamic magnetic reversal. The domain walls form near by the middle plane of a ribbon and move to its opposite main surfaces with different velocities.

  5. Magnetization switching behavior with competing anisotropies in epitaxial Co3FeN /MnN exchange-coupled bilayers

    Science.gov (United States)

    Hajiri, T.; Yoshida, T.; Jaiswal, S.; Filianina, M.; Borie, B.; Ando, H.; Asano, H.; Zabel, H.; Kläui, M.

    2016-11-01

    We report unusual magnetization switching processes and angular-dependent exchange bias effects in fully epitaxial Co3FeN /MnN bilayers, where magnetocrystalline anisotropy and exchange coupling compete, probed by longitudinal and transverse magneto-optic Kerr effect (MOKE) magnetometry. The MOKE loops show multistep jumps corresponding to the nucleation and propagation of 90∘ domain walls in as-grown bilayers. By inducing exchange coupling, we confirm changes of the magnetization switching process due to the unidirectional anisotropy field of the exchange coupling. Taking into account the experimentally obtained values of the fourfold magnetocrystalline anisotropy, the unidirectional anisotropy field, the exchange-coupling constant, and the uniaxial anisotropy including its direction, the calculated angular-dependent exchange bias reproduces the experimental results. These results demonstrate the essential role of the competition between magnetocrystalline anisotropy and exchange coupling for understanding and tailoring exchange-coupling phenomena usable for engineering switching in fully epitaxial bilayers made of tailored materials.

  6. Tilted spin torque-driven ferromagnetic resonance in a perpendicular-analyzer magnetic trilayer

    International Nuclear Information System (INIS)

    Wang Rixing; He Pengbin; Liu Quanhui; Li Zaidong; Pan Anlian; Zou Bingsuo; Wang Yanguo

    2010-01-01

    A theoretical study is presented on the current-driven ferromagnetic resonance in the magnetic trilayers. On the basis of the Landau-Lifshitz-Gilbert-Slonczewski equation, we derive the output dc voltage for arbitrary anisotropy in the free and pinned layers by the linearization method. As an example, the resonance spectra of the tilted-polarizer and perpendicular-analyzer trilayer show that the equilibrium position, the resonant linewidth and the resonant location can be tuned by changing the magnitude and the direction of spin torque. The effective damping can be minimized through adjusting the current and the pinned-layer magnetization direction.

  7. Momentum transfer resolved memory in a magnetic system with perpendicular anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Seu, Keoki; Roy, Sujoy; Su, Run; Parks, Daniel; Shipton, Erik; Fullerton, Eric; Kevan, Stephen

    2011-01-28

    We have used resonant, coherent soft x-ray scattering to measure wave vector re- solved magnetic domain memory in Co/Pd multilayers. The technique uses angular cross correlation functions and can be applied to any system with circular annuli of constant values of scattering wave vector q. In our Co/Pd film, the memory exhibits a maximum at q = 0.0384 nm-1 near initial reversal that decreases in magnitude as the magnetization is further reversed. The peak is attributed to bubble domains that nucleate reproducibly near initial reversal and which grow into a labyrinth domain structure that is not reproduced from one magnetization cycle to the next.

  8. Phenomenological description of anisotropy effects in some ferromagnetic superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Shopova, Diana V., E-mail: sho@issp.bas.bg [TCCM Research Group, Institute of Solid State Physics, Bulgarian Academy of Sciences, BG-1784 Sofia (Bulgaria); Todorov, Michail D. [Department of Applied Mathematics and Computer Science, Technical University of Sofia, 1000 Sofia (Bulgaria)

    2015-07-03

    We study phenomenologically the role of anisotropy in ferromagnetic superconductors UGe{sub 2}, URhGe, and UCoGe for the description of their phase diagrams. We use the Ginzburg–Landau free energy in its uniform form as we will consider only spatially independent solutions. This is an expansion of previously derived results where the effect of Cooper-pair and crystal anisotropies is not taken into account. The three compounds are separately discussed with the special stress on UGe{sub 2}. The main effect comes from the strong uniaxial anisotropy of magnetization while the anisotropy of Cooper pairs and crystal anisotropy only slightly change the phase diagram in the vicinity of Curie temperature. The limitations of this approach are also discussed. - Highlights: • Anisotropic Landau energy for description of ferromagnetic superconductors is proposed. • Meissner phases are described with their existence and stability conditions. • The application of the model to UGe{sub 2} is discussed. • The limitations to apply the model for description of experimental data are explained.

  9. Monolayer Boron Nitride Substrate Interactions with Graphene Under In-Plane and Perpendicular Strains: A First-Principles Study

    Science.gov (United States)

    Behzad, Somayeh

    2018-04-01

    Effects of strain on the electronic and optical properties of graphene on monolayer boron nitride (BN) substrate are investigated using first-principle calculations based on density functional theory. Strain-free graphene/BN has a small band gap of 97 meV at the K point. The magnitude of band gap increases with in-plane biaxial strain while it decreases with the perpendicular uniaxial strain. The ɛ2 (ω ) spectrum of graphene/BN bilayer for parallel polarization shows red and blue shifts by applying the in-plane tensile and compressive strains, respectively. Also the positions of peaks in the ɛ2 (ω ) spectrum are not significantly changed under perpendicular strain. The calculated results indicate that graphene on the BN substrate has great potential in microelectronic and optoelectronic applications.

  10. Influence of deposition field on the magnetic anisotropy in epitaxial Co70Fe30 films on GaAs(001)

    International Nuclear Information System (INIS)

    Hindmarch, A.T.; Arena, D.; Dempsey, K.J.; Henini, M.; Marrows, C.H.

    2010-01-01

    The effect of the application of a magnetic field during deposition of epitaxial Co 70 Fe 30 onto GaAs(001) is shown; we find an initially counterintuitive result. For field applied along the interfacial uniaxial hard axis the relative effective uniaxial magnetic anisotropy is increased by a factor of two in comparison to both field along the uniaxial easy axis, or no field; usually, application of a deposition field results in a uniaxial easy axis parallel to this field direction. We show that the deposition field changes the maximal projection of the atomic orbital magnetic moments onto the easy axis, which corresponds to a deposition field induced shift in the Helmholtz free-energy landscape of the system.

  11. Long-wavelength optical phonon behavior in uniaxial strained graphene: Role of electron-phonon interaction

    Science.gov (United States)

    Assili, M.; Haddad, S.

    2014-09-01

    We derive the frequency shifts and the broadening of Γ-point longitudinal optical (LO) and transverse optical (TO) phonon modes, due to electron-phonon interaction, in graphene under uniaxial strain as a function of the electron density and the disorder amount. We show that, in the absence of a shear strain component, such interaction gives rise to a lifting of the degeneracy of the LO and TO modes which contributes to the splitting of the G Raman band. The anisotropy of the electronic spectrum, induced by the strain, results in a polarization dependence of the LO and TO modes. This dependence is in agreement with the experimental results showing a periodic modulation of the Raman intensity of the split G peak. Moreover, the anomalous behavior of the frequency shift reported in undeformed graphene is found to be robust under strain.

  12. Nanosized perpendicular organic spin-valves

    Energy Technology Data Exchange (ETDEWEB)

    Göckeritz, Robert; Homonnay, Nico; Müller, Alexander; Richter, Tim [Institut für Physik, Martin Luther University Halle-Wittenberg, 06099 Halle (Saale) (Germany); Fuhrmann, Bodo [Interdisziplinäres Zentrum für Materialwissenschaften, Martin Luther University Halle-Wittenberg, 06099 Halle (Saale) (Germany); Schmidt, Georg, E-mail: georg.schmidt@physik.uni-halle.de [Institut für Physik, Martin Luther University Halle-Wittenberg, 06099 Halle (Saale) (Germany); Interdisziplinäres Zentrum für Materialwissenschaften, Martin Luther University Halle-Wittenberg, 06099 Halle (Saale) (Germany)

    2015-03-09

    A fabrication process for perpendicular organic spin-valve devices based on the organic semiconductor Alq3 has been developed which offers the possibility to achieve active device areas of less than 500 × 500 nm{sup 2} and is flexible in terms of material choice for the active layers. Characterization of the resulting devices shows a large magnetoresistance of sometimes more than 100%, however with equally large variation from device to device. Comparison with large area spin-valves indicates that the magnetoresistance of both large and small devices most likely originates from tunneling through pinholes and tunneling magnetoresistance.

  13. Perpendicular exchange coupling effects in ferrimagnetic TbFeCo/GdFeCo hard/soft structures

    Science.gov (United States)

    Wang, Ke; Wang, Yahong; Ling, Fujin; Xu, Zhan

    2018-04-01

    Bilayers consisting of magnetically hard TbFeCo and soft GdFeCo alloy were fabricated. Exchange-spring and sharp switching in a step-by-step fashion were observed in the TbFeCo/GdFeCo hard/soft bilayers with increasing GdFeCo thickness. A perpendicular exchange bias field of several hundred Oersteds is observed from the shift of minor loops pinned by TbFeCo layer. The perpendicular exchange energy is derived to be in the range of 0.18-0.30 erg/cm2. The exchange energy is shown to increase with the thickness of GdFeCo layer in the bilayers, which can be attributed to the enhanced perpendicular anisotropy of GdFeCo layer in our experimental range.

  14. Domain engineering of the metastable domains in the 4f-uniaxial-ferromagnet CeRu2Ga2B

    Science.gov (United States)

    Wulferding, D.; Kim, H.; Yang, I.; Jeong, J.; Barros, K.; Kato, Y.; Martin, I.; Ayala-Valenzuela, O. E.; Lee, M.; Choi, H. C.; Ronning, F.; Civale, L.; Baumbach, R. E.; Bauer, E. D.; Thompson, J. D.; Movshovich, R.; Kim, Jeehoon

    2017-04-01

    In search of novel, improved materials for magnetic data storage and spintronic devices, compounds that allow a tailoring of magnetic domain shapes and sizes are essential. Good candidates are materials with intrinsic anisotropies or competing interactions, as they are prone to host various domain phases that can be easily and precisely selected by external tuning parameters such as temperature and magnetic field. Here, we utilize vector magnetic fields to visualize directly the magnetic anisotropy in the uniaxial ferromagnet CeRu2Ga2B. We demonstrate a feasible control both globally and locally of domain shapes and sizes by the external field as well as a smooth transition from single stripe to bubble domains, which opens the door to future applications based on magnetic domain tailoring.

  15. Uniaxial ratcheting behavior of Zircaloy-4 tubes at room temperature

    International Nuclear Information System (INIS)

    Wen, Mingjian; Li, Hua; Yu, Dunji; Chen, Gang; Chen, Xu

    2013-01-01

    In this study, a series of uniaxial tensile, strain cycling and uniaxial ratcheting tests were conducted at room temperature on Zircaloy-4 (Zr-4) tubes used as nuclear fuel cladding in Pressurized Water Reactors (PWRs) for the purpose to investigate the uniaxial ratcheting behavior of Zr-4 and the factors which may influence it. The experimental results show that at room temperature this material features cyclic softening remarkably within the strain range of 1.6%, and former cycling under larger strain amplitude cannot retard cyclic softening of later cycling under lower strain amplitude. Uniaxial ratcheting strain accumulates in the direction of mean stress, and the ratcheting stain level is larger under tensile mean stress than that under compressive mean stress. Uniaxial ratcheting strain level increases with the increase of mean stress and stress amplitude, and decreases with the increase of loading rate. The sequence of loading rate appears to have no effects on the final ratcheting strain accumulation. Loading history has great influence on the uniaxial ratcheting behavior. Lower stress level after loading history with higher stress level leads to the shakedown of ratcheting. Higher loading rate after loading history with lower loading rate brings down the ratcheting strain rate. Uniaxial ratcheting behavior is sensitive to compressive pre-strain, and the decay rate of the ratcheting strain rate is slowed down by pre-compression

  16. Determination of the out-of-plane anisotropy contributions (first and second anisotropy terms) in amorphous Nd-Co thin films by micromagnetic numerical simulations

    Science.gov (United States)

    Alvarez-Prado, L. M.; Cid, R.; Morales, R.; Diaz, J.; Vélez, M.; Rubio, H.; Hierro-Rodriguez, A.; Alameda, J. M.

    2018-06-01

    Amorphous Nd-Co thin films exhibit stripe shaped periodic magnetic domains with local out-of-plane magnetization components due to their perpendicular magnetic anisotropy. This anisotropy has been quantified in a fairly simple way by reproducing the experimental magnetization curves by means of micromagnetic numerical simulations. The simulations show that the first (K1) and second (K2) anisotropy constants must be used to properly describe the variation of the stripe domains with the in plane applied magnetic field. A strong temperature dependence of both K1 and K2 has been obtained between 10 K and room temperature. This anisotropy behavior is characteristic of two magnetically coupled 3d-4f sublattices with competing anisotropies.

  17. Perpendicular relativistic shocks in magnetized pair plasma

    Science.gov (United States)

    Plotnikov, Illya; Grassi, Anna; Grech, Mickael

    2018-04-01

    Perpendicular relativistic (γ0 = 10) shocks in magnetized pair plasmas are investigated using two dimensional Particle-in-Cell simulations. A systematic survey, from unmagnetized to strongly magnetized shocks, is presented accurately capturing the transition from Weibel-mediated to magnetic-reflection-shaped shocks. This transition is found to occur for upstream flow magnetizations 10-3 10-2, it leaves place to a purely electromagnetic precursor following from the strong emission of electromagnetic waves at the shock front. Particle acceleration is found to be efficient in weakly magnetized perpendicular shocks in agreement with previous works, and is fully suppressed for σ > 10-2. Diffusive Shock Acceleration is observed only in weakly magnetized shocks, while a dominant contribution of Shock Drift Acceleration is evidenced at intermediate magnetizations. The spatial diffusion coefficients are extracted from the simulations allowing for a deeper insight into the self-consistent particle kinematics and scale with the square of the particle energy in weakly magnetized shocks. These results have implications for particle acceleration in the internal shocks of AGN jets and in the termination shocks of Pulsar Wind Nebulae.

  18. Perpendicularity misjudgments caused by contextual stimulus elements.

    Science.gov (United States)

    Bulatov, Aleksandr; Bulatova, Natalija; Surkys, Tadas

    2012-10-15

    It has been demonstrated in previous studies that the illusions of extent of the Brentano type can be explained by the perceptual positional shifts of the stimulus terminators in direction of the centers-of-masses (centroids) of adjacent contextual flanks [Bulatov, A. et al. (2011). Contextual flanks' tilting and magnitude of illusion of extent. Vision Research, 51(1), 58-64]. In the present study, the applicability of the centroid approach to explain the right-angle misjudgments was tested psychophysically using stimuli composed of three small disks (dots) forming an imaginary rectangular triangle. Stimuli comprised the Müller-Lyer wings or line segments (bars) as the contextual distracters rotated around the vertices of the triangle, and changes in the magnitude of the illusion of perpendicularity were measured in a set of experiments. A good resemblance between the experimental data and theoretical predictions obtained strongly supports the suggestion regarding the common "centroid" origin of the illusions of extent of the Brentano type and misperception of the perpendicularity investigated. 2012 Elsevier Ltd. All rights reserved

  19. Thickness dependence of magnetic anisotropy and domains in amorphous Co{sub 40}Fe{sub 40}B{sub 20} thin films grown on PET flexible substrates

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Zhenhua, E-mail: tangzhenhua1988@163.com [Guangdong Provincial Key Laboratory of Functional Soft Condensed Matter, School of Materials and Energy, Guangdong University of Technology, Guangzhou 510006 (China); Department of Physics, The University of Hong Kong, Pokfulam Road, Hong Kong (China); Ni, Hao [Department of Physics, The University of Hong Kong, Pokfulam Road, Hong Kong (China); College of science, China university of petroleum, Qingdao, Shandong 266580 China (China); Lu, Biao [Guangdong Provincial Key Laboratory of Functional Soft Condensed Matter, School of Materials and Energy, Guangdong University of Technology, Guangzhou 510006 (China); Zheng, Ming [Department of Physics, The University of Hong Kong, Pokfulam Road, Hong Kong (China); Huang, Yong-An [Guangdong Provincial Key Laboratory of Functional Soft Condensed Matter, School of Materials and Energy, Guangdong University of Technology, Guangzhou 510006 (China); Lu, Sheng-Guo, E-mail: sglu@gdut.edu.cn [Guangdong Provincial Key Laboratory of Functional Soft Condensed Matter, School of Materials and Energy, Guangdong University of Technology, Guangzhou 510006 (China); Tang, Minghua [Key Laboratory of Low Dimensional Materials and Application Technology, Ministry of Education (Xiangtan University), Xiangtan, Hunan 411105 (China); Gao, Ju [Department of Physics, The University of Hong Kong, Pokfulam Road, Hong Kong (China)

    2017-03-15

    The amorphous Co{sub 40}Fe{sub 40}B{sub 20} (CoFeB) films (5–200 nm in thickness) were grown on flexible polyethylene terephthalate (PET) substrates using the DC magnetron-sputtering method. The thickness dependence of structural and magnetic properties of flexible CoFeB thin films was investigated in detail. The in-plane uniaxial magnetic anisotropy induced by strain as a function of thickness was obtained in flexible CoFeB thin films, and a critical thickness of ~150 nm for in-plane magnetic anisotropy was observed. Moreover, the domains and the uniaxial anisotropy as a function of angular direction of applied magnetic field were characterized. The results show potential for designing CoFeB-based flexible spintronic devices in which the physical parameters could be tailored by controlling the thickness of the thin film. - Graphical abstract: The in-plane uniaxial magnetic anisotropy induced by strain as a function of thickness was obtained in flexible CoFeB thin films, and a critical thickness of ~150 nm for in-plane magnetic anisotropy was observed. Moreover, the domains and the uniaxial anisotropy as a function of angular direction of applied magnetic field were characterized. - Highlights: • The thickness effect on the magnetic properties in amorphous CoFeB thin films grown on flexible substrates was investigated. • The in-plane uniaxial magnetic anisotropy induced by strains was observed. • A critical thickness of ~ 150 nm for the flexible CoFeB thin film on PET substrate was obtained.

  20. Magnetic anisotropy of (Sm, Y)2Fe17Ny compounds

    International Nuclear Information System (INIS)

    Lu, Y.; Tegus, O.; Li, Q.A.; Tang, N.; Yu, M.J.; Zhao, R.W.; Kuang, J.P.; Yang, F.M.; Zhou, G.F.; Li, X.; Boer, F.R. de

    1992-01-01

    A study of the crystal structure and the magnetic properties, especially the magnetocrystalline anisotropy of (Sm 1-x Y x ) 2 Fe 17 N y compounds (x = 0, 0.2, 0.4, 0.6, 0.8, and 1.0, 2 2 Zn 17 - or Th 2 Ni 17 -type structure as the original compounds. The Curie temperatures decrease from 750 to 700 K as x increases from 0 to 1. The anisotropy field decreases linearly with increasing yttrium content. The spin reorientation has been investigated by means of high field magnetization measurements, AC-susceptibility measurements and thermomagnetic analysis, combined with X-ray diffraction. The anisotropy constants K 1 , K 2 and K 3 were derived by a phenomenological analysis, using magnetization curves measured in high fields, applied perpendicular to the alignment direction of the powder samples. A tentative spin phase diagram of the series is presented. (orig.)

  1. Ion temperature anisotropy limitation in high beta plasmas

    International Nuclear Information System (INIS)

    Scime, Earl E.; Keiter, Paul A.; Balkey, Matthew M.; Boivin, Robert F.; Kline, John L.; Blackburn, Melanie; Gary, S. Peter

    2000-01-01

    Measurements of parallel and perpendicular ion temperatures in the Large Experiment on Instabilities and Anisotropies (LEIA) space simulation chamber display an inverse correlation between the upper bound on the ion temperature anisotropy and the parallel ion beta (β=8πnkT/B 2 ). Fluctuation measurements indicate the presence of low frequency, transverse, electromagnetic waves with wave numbers and frequencies that are consistent with predictions for Alfven Ion Cyclotron instabilities. These observations are also consistent with in situ spacecraft measurements in the Earth's magnetosheath and with a theoretical/computational model that predicts that such an upper bound on the ion temperature anisotropy is imposed by scattering from enhanced fluctuations due to growth of the Alfven ion cyclotron instability. (c) 2000 American Institute of Physics

  2. Determination of anisotropy constants of protein encapsulated iron oxide nanoparticles by electron magnetic resonance

    International Nuclear Information System (INIS)

    Li Hongyan; Klem, Michael T.; Sebby, Karl B.; Singel, David J.; Young, Mark; Douglas, Trevor; Idzerda, Yves U.

    2009-01-01

    Angle-dependent electron magnetic resonance was performed on 4.9, 8.0, and 19 nm iron oxide nanoparticles encapsulated within protein capsids and suspended in water. Measurements were taken at liquid nitrogen temperature after cooling in a 1 T field to partially align the particles. The angle dependence of the shifts in the resonance field for the iron oxide nanoparticles (synthesized within Listeria-Dps, horse spleen ferritin, and cowpea chlorotic mottle virus) all show evidence of a uniaxial anisotropy. Using a Boltzmann distribution for the particles' easy-axis direction, we are able to use the resonance field shifts to extract a value for the anisotropy energy, showing that the anisotropy energy density increases with decreasing particle size. This suggests that surface anisotropy plays a significant role in magnetic nanoparticles of this size

  3. Determination of anisotropy constants of protein encapsulated iron oxide nanoparticles by electron magnetic resonance

    Energy Technology Data Exchange (ETDEWEB)

    Li Hongyan [Department of Physics, Montana State University, Bozeman, MT 59717 (United States); Center for Bio-Inspired Nanomaterials, Montana State University, Bozeman, MT 59717 (United States); Klem, Michael T.; Sebby, Karl B.; Singel, David J. [Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59717 (United States); Center for Bio-Inspired Nanomaterials, Montana State University, Bozeman, MT 59717 (United States); Young, Mark [Department of Plant Sciences and Plant Pathology, Montana State University, Bozeman, MT 59717 (United States); Center for Bio-Inspired Nanomaterials, Montana State University, Bozeman, MT 59717 (United States); Douglas, Trevor [Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59717 (United States); Center for Bio-Inspired Nanomaterials, Montana State University, Bozeman, MT 59717 (United States); Idzerda, Yves U. [Department of Physics, Montana State University, Bozeman, MT 59717 (United States); Center for Bio-Inspired Nanomaterials, Montana State University, Bozeman, MT 59717 (United States)], E-mail: Idzerda@montana.edu

    2009-02-15

    Angle-dependent electron magnetic resonance was performed on 4.9, 8.0, and 19 nm iron oxide nanoparticles encapsulated within protein capsids and suspended in water. Measurements were taken at liquid nitrogen temperature after cooling in a 1 T field to partially align the particles. The angle dependence of the shifts in the resonance field for the iron oxide nanoparticles (synthesized within Listeria-Dps, horse spleen ferritin, and cowpea chlorotic mottle virus) all show evidence of a uniaxial anisotropy. Using a Boltzmann distribution for the particles' easy-axis direction, we are able to use the resonance field shifts to extract a value for the anisotropy energy, showing that the anisotropy energy density increases with decreasing particle size. This suggests that surface anisotropy plays a significant role in magnetic nanoparticles of this size.

  4. Optical anisotropy induced by mechanical strain around the fundamental gap of GaAs

    Energy Technology Data Exchange (ETDEWEB)

    Ortega-Gallegos, J.; Lastras-Martinez, A.; Lastras-Martinez, L.F. [Instituto de Investigacion en Comunicacion Optica, Universidad Autonoma de San Luis Potosi, Alvaro Obregon 64, San Luis Potosi (Mexico); Balderas-Navarro, R.E. [Instituto de Investigacion en Comunicacion Optica, Universidad Autonoma de San Luis Potosi, Alvaro Obregon 64, San Luis Potosi (Mexico); Facultad de Ciencias, Universidad Autonoma de San Luis Potosi, Alvaro Obregon 64, San Luis Potosi (Mexico)

    2008-07-01

    We report on a theoretical-experimental study of reflectance anisotropy spectroscopy (RAS) of GaAs (001) crystals under uniaxial stress. The study was carried out in the energy region around the fundamental transition. RAS spectra in the energy range from 1.2-1.7 eV were measured with a photoelastic-modulator-based spectrometer. To induce an optical anisotropy, the GaAs crystals were thinned down to 400 {mu}m and an calibrated uniaxial stress was applied by deflection. RAS showed a line shape consisting of an oscillation at around E{sub 0}. On the basis of a perturbative approach employing the Pikus-Bir Hamiltonian, we calculated the RAS line shape and found a close agreement with the experimental spectra. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  5. Anisotropy, magnetic field and stress influences on the phase transitions on spin-flop-type antiferromagnets

    International Nuclear Information System (INIS)

    Machado, S.F.; Espirito Santo Univ., Vitoria; Tsallis, C.

    1983-01-01

    Within a mean field approximation, the influences of anisotropy (in the spin space) and external uniaxial stress on the Heisenberg antiferromagnet in the presence of magnetic field are discussed. The phase diagram evolution (as function of anisotropy and stress) which is obtained, enables a satisfactory overall interpretation of recent experiments on Mn(Br sub(1-x) Cl sub(x)) 2 .4H 2 O, K 2 [FeCl 5 (H 2 O)], CoCl 2 .6H 2 O and (C 2 H 5 NH 3 ) 2 CuCl 4 . (Author) [pt

  6. Analysis of electromagnetic scattering by uniaxial anisotropic bispheres.

    Science.gov (United States)

    Li, Zheng-Jun; Wu, Zhen-Sen; Li, Hai-Ying

    2011-02-01

    Based on the generalized multiparticle Mie theory and the Fourier transformation approach, electromagnetic (EM) scattering of two interacting homogeneous uniaxial anisotropic spheres with parallel primary optical axes is investigated. By introducing the Fourier transformation, the EM fields in the uniaxial anisotropic spheres are expanded in terms of the spherical vector wave functions. The interactive scattering coefficients and the expansion coefficients of the internal fields are derived through the continuous boundary conditions on which the interaction of the bispheres is considered. Some selected calculations on the effects of the size parameter, the uniaxial anisotropic absorbing dielectric, and the sphere separation distance are described. The backward radar cross section of two uniaxial anisotropic spheres with a complex permittivity tensor changing with the sphere separation distance is numerically studied. The authors are hopeful that the work in this paper will help provide an effective calibration for further research on the scattering characteristic of an aggregate of anisotropic spheres or other shaped anisotropic particles.

  7. Fatigue in tension perpendicular to the grain

    DEFF Research Database (Denmark)

    Clorius, Christian Odin; Pedersen, Martin Bo Uhre; Hoffmeyer, Preben

    1999-01-01

    Traditinally fatigue resistance is quantified as number of cycles to failure at a given stress level. A previous study by the authors showed that fatigue in compression parallel to the grain is governed partly by duration of load and partly by an effect of loading, i.e. a combination of a creep...... mechanism and a mechanism connected to damage introduce in the loading sequences. The purpose of the present study is to disentangle the effect of duration of load from the effect of load oscillation in fatigue in tension perpendicular to the grain. Fatigue experiments are made on small specimens...... and on dowel type joints with slotted in steel plates. In series of ten, the small specimens are taken to fatigue failure in uniform tension at square wave shaped load cycles at 0.01 Hz and 0.1 Hz. In order to test the predictive validity of the result from the small tension specimens, fatigue experiments...

  8. Fatigue In Tension Perpendicular to the Grain

    DEFF Research Database (Denmark)

    Clorius, Christian Odin; Pedersen, Martin Uhre; Hoffmeyer, Preben

    2004-01-01

    Traditionally fatigue resistance is quantified as number of cycles to failure at a given stress level. A previous study by the authors showed that fatigue in compression parallel to the grain is governed partly by duration of load and partly by an effect of loading, i.e. a combination of a creep...... mechanism and a mechanism connected to damage introduced in the loading sequences. The purpose of the present study is to disentangle the effect of duration of load from the effect of load oscillation in fatigue in tension perpendicular to the grain. Fatigue experiments are made on small specimens...... and on dowel type joints with slotted in steel plates. In series of ten, the small specimens are taken to fatigue failure in uniform tension at square wave shaped load cycles at 0.01 Hz and 0.1 Hz. In arder to test the predictive validity of the result from the small tension specimens, fatigue experiments...

  9. Counterstreaming magnetized plasmas. II. Perpendicular wave propagation

    International Nuclear Information System (INIS)

    Tautz, R.C.; Schlickeiser, R.

    2006-01-01

    The properties of longitudinal and transverse oscillations in magnetized symmetric counterstreaming Maxwellian plasmas with equal thermal velocities for waves propagating perpendicular to the stream direction are investigated on the basis of Maxwell equations and the nonrelativistic Vlasov equation. With the constraint of vanishing particle flux in the stream direction, three distinct dispersion relations are known, which are the ordinary-wave mode, the Bernstein wave mode, and the extraordinary electromagnetic wave mode, where the latter two are only approximations. In this article, all three dispersion relations are evaluated for a counterstreaming Maxwellian distribution function in terms of the hypergeometric function 2 F 2 . The growth rates for the ordinary-wave mode are compared to earlier results by Bornatici and Lee [Phys. Fluids 13, 3007 (1970)], who derived approximate results, whereas in this article the exact dispersion relation is solved numerically. The original results are therefore improved and show differences of up to 21% to the results obtained in this article

  10. Recording performances in perpendicular magnetic patterned media

    International Nuclear Information System (INIS)

    Asbahi, M; Moritz, J; Dieny, B; Gourgon, C; Perret, C; Van de Veerdonk, R J M

    2010-01-01

    We report on the recording performances and signal-to-noise ratio (SNR) analyses of perpendicular magnetic bit-patterned media. Two different types of magnetic samples are investigated. They differ by the way that they were patterned (nano-imprint versus e-beam lithography) as well as their magnetic properties (Co/Pt multilayers and CoCrPt alloy are the recording layers).Using a contact read/write quasi-static tester, we were able to characterize the write windows, the bit error rates and measure the SNR. The influence of magnetic properties and media microstructure on the writing processes is studied. We show also that the lithographical method used to replicate the media induces more or less noise due to structural distributions.

  11. Tuning stress-induced magnetic anisotropy and high frequency properties of FeCo films deposited on different curvature substrates

    International Nuclear Information System (INIS)

    Wang, Z.K.; Feng, E.X.; Liu, Q.F.; Wang, J.B.; Xue, D.S.

    2012-01-01

    It is important to control magnetic anisotropy of ferromagnetic materials. In this work, FeCo thin films are deposited on the curving substrates by electrochemical deposition to adjust the stress-induced magnetic anisotropy. The compressive stress is produced in the as-deposited films after the substrates are flattened. A simplified theoretical model of ferromagnetic resonance is utilized to measure the intrinsic magnetic anisotropy field and saturation magnetization. The results show that the stress-induced magnetic anisotropy and the resonance frequency increase with the increase of substrate curvature. The induced easy axis is perpendicular to the compressive stress direction.

  12. Anisotropic perpendicular axis magnetostriction in twinned TbxDy1-xFe1.95

    International Nuclear Information System (INIS)

    Teter, J.P.; Wun-Fogle, M.; Clark, A.E.; Mahoney, K.

    1990-01-01

    The longitudinal magnetostriction (Δl/l) for twinned Tb x Dy 1-x Fe 1.95 material, prepared by the free-standing float-zone method, has been previously measured and found to be very large (2000x10 -6 ) at room temperature. The magnetostrictions for the [111] and [1 bar 10] crystallographic axes perpendicular to the applied stress and magnetic-field [11 bar 2] direction are presented as functions of temperature, applied stress, and applied magnetic field. The temperature range is ±60 degree C centered about the anisotropy compensation temperature of Terfenol-D (+10 degree C). The stress ranges from 2 to 32 MPa and the magnetic field to ±2000 Oe. The temperature dependence of the perpendicular axes magnetostriction is similar to that of the conventional magnetostriction measured parallel to the [11 bar 2] growth axis. Relative values for the saturation magnetostriction exhibit a large anisotropy in the perpendicular direction, ranging from -117% for the [111] to +19% for the [1 bar 10] direction. This ratio stays constant as a function of temperature above the compensation temperature for a given prestress above 8 MPa. The largest absolute value of magnetostriction (2260x10 -6 ) occurs in the [111] direction at 10 degree C at a prestress pressure of 12 MPa. Above this temperature the magnetostriction falls at a rate of -8.5x10 -6 /degree C. The volume magnetostriction is shown to be small and highly sample dependent. All data is consistent with the parent-twin magnetization model and also the magnetostriction values along nonprincipal axes

  13. Perpendicular magnetic tunnel junction with thin CoFeB/Ta/Co/Pd/Co reference layer

    Energy Technology Data Exchange (ETDEWEB)

    Gan, Huadong, E-mail: huadong@avalanche-technology.com; Malmhall, Roger; Wang, Zihui; Yen, Bing K; Zhang, Jing; Wang, Xiaobin; Zhou, Yuchen; Hao, Xiaojie; Jung, Dongha; Satoh, Kimihiro; Huai, Yiming [Avalanche Technology, 46600 Landing Parkway, Fremont, California 94538 (United States)

    2014-11-10

    Integration of high density spin transfer torque magnetoresistance random access memory requires a thin stack (less than 15 nm) of perpendicular magnetic tunnel junction (p-MTJ). We propose an innovative approach to solve this challenging problem by reducing the thickness and/or moment of the reference layer. A thin reference layer structure of CoFeB/Ta/Co/Pd/Co has 60% magnetic moment of the conventional thick structure including [Co/Pd] multilayers. We demonstrate that the perpendicular magnetization of the CoFeB/Ta/Co/Pd/Co structure can be realized by anti-ferromagnetically coupling to a pinned layer with strong perpendicular anisotropy via Ruderman-Kittel-Kasuya-Yosida exchange interaction. The pMTJ with thin CoFeB/Ta/Co/Pd/Co reference layer has a comparable TMR ratio (near 80%) as that with thick reference layer after annealing at 280 °C. The pMTJ with thin reference layer has a total thickness less than 15 nm, thereby significantly increasing the etching margin required for integration of high density pMTJ array on wafers with form factor of 300 mm and beyond.

  14. Variable substrate temperature deposition of CoFeB film on Ta for manipulating the perpendicular coercive forces

    Science.gov (United States)

    Lakshmanan, Saravanan; Rao, Subha Krishna; Muthuvel, Manivel Raja; Chandrasekaran, Gopalakrishnan; Therese, Helen Annal

    2017-08-01

    Magnetization of Ta/CoFeB/Ta trilayer films with thick layer of CoFeB deposited under different substrate temperatures (Ts) via ultra-high vacuum DC sputtering technique has been measured with the applied magnetic field parallel and perpendicular to the plane of the film respectively to study the perpendicular coercive forces of the film. The samples were further analyzed for its structural, topological, morphological, and electrical transport properties. The core chemical states for the elements present in the CoFeB thin film were analyzed by XPS studies. Magnetization studies reveal the existence of perpendicular coercive forces in CoFeB films deposited only at certain temperatures such as RT, 450 °C, 475 °C and 500 °C. CoFeB film deposited at 475 °C exhibited a maximum coercivity of 315 Oe and a very low saturation magnetization (Ms) of 169 emu/cc in perpendicular direction. This pronounced effect in perpendicular coercive forces observed for CoFeB475 could be attributed to the effect of temperature in enhancing the crystallization of the film at the Ta/CoFeB interfaces. However at temperatures higher than 475 °C the destruction of the Ta/CoFeB interface due to intermixing of Ta and CoFeB results in the disappearance of magnetic anisotropy.

  15. Electrical anisotropy in the presence of oceans—a sensitivity study

    Science.gov (United States)

    Cembrowski, Marcel; Junge, Andreas

    2018-05-01

    Electrical anisotropy in the presence of oceans is particularly relevant at continent-ocean subduction zones (e.g. Cascadian and Andean Margin), where seismic anisotropy has been found with trench-parallel or perpendicular fast direction. The identification of electrical anisotropy at such locations sheds new light on the relation between seismic and electrical anisotropies. At areas confined by two opposite oceans, for example the Pyrenean Area and Central America, we demonstrate that the superposed responses of both oceans generate a uniform and large phase split of the main phase tensor axes. The pattern of the tipper arrows is comparatively complicated and it is often difficult to associate their length and orientation to the coast effect. On the basis of simple forward models involving opposite oceans and anisotropic layers, we show that both structures generate similar responses. In the case of a deep anisotropic layer, the resistivity and phase split generated by the oceans alone will be increased or decreased depending on the azimuth of the conducting horizontal principal axes. The 3-D isotropic inversion of the anisotropic forward responses reproduces the input data reasonably well. The anisotropy is explained by large opposed conductors outside the station grid and by tube-like elongated conductors representing a macroscopic anisotropy. If the conductive direction is perpendicular to the shorelines, the anisotropy is not recovered by 3-D isotropic inversion.

  16. Effect of Pressure Anisotropy on the m = 1 Small Wavelength Modes in Z-Pinches

    Science.gov (United States)

    Faghihi, M.

    1987-05-01

    A generalization of Freidberg's perpendicular MHD model is used to investigate the effect of pressure anisotropy on the small wavelength internal kink (m = 1) mode instability in a Z-Pinch. A normal mode analysis of perturbed motion of an incompressible, collisionless and cylindrical plasma is performed. The stability criterion is (rΣB2)' = 0.

  17. Role of the substrate on the magnetic anisotropy of magnetite thin films grown by ion-assisted deposition

    International Nuclear Information System (INIS)

    Prieto, Pilar; Prieto, José Emilio; Gargallo-Caballero, Raquel; Marco, José Francisco; Figuera, Juan de la

    2015-01-01

    Graphical abstract: - Highlights: • The magnetic anisotropy of magnetite thin films is controlled by the substrate induced microstructure. • Single-crystal oxide substrates induce fourfold in-plane magnetic anisotropy • MgO and SrTiO_3 substrates show the same magnetic behavior despite its different mismatch with Fe_3O_4 films. • Silicon and glass substrates induce in-plane magnetic isotropy and uniaxial anisotropy, respectively. - Abstract: Magnetite (Fe_3O_4) thin films were deposited on MgO (0 0 1), SrTiO_3 (0 0 1), LaAlO_3 (0 0 1) single crystal substrates as well on as silicon and amorphous glass in order to study the effect of the substrate on their magnetic properties, mainly the magnetic anisotropy. We have performed a structural, morphological and compositional characterization by X-ray diffraction, atomic force microscopy and Rutherford backscattering ion channeling in oxygen resonance mode. The magnetic anisotropy has been investigated by vectorial magneto-optical Kerr effect. The results indicate that the magnetic anisotropy is especially influenced by the substrate-induced microstructure. In-plane isotropy and uniaxial anisotropy behavior have been observed on silicon and glass substrates, respectively. The transition between both behaviors depends on grain size. For LaAlO_3 substrates, in which the lattice mismatch between the Fe_3O_4 films and the substrate is significant, a weak in-plane fourfold magnetic anisotropy is induced. However when magnetite is deposited on MgO (0 0 1) and SrTiO_3 (0 0 1) substrates, a well-defined fourfold in-plane magnetic anisotropy is observed with easy axes along [1 0 0] and [0 1 0] directions. The magnetic properties on these two latter substrates are similar in terms of magnetic anisotropy and coercive fields.

  18. Perpendicular magnetic recording-Its development and realization

    Energy Technology Data Exchange (ETDEWEB)

    Iwasaki, Shun-ichi, E-mail: iwasaki@tohtech.ac.jp [Tohoku Institute of Technology, 35-1 Yagiyamakasumi-cho, Taihaku-ku, Sendai 982-8577 (Japan)

    2012-02-15

    Development of perpendicular magnetic recording is summarized along with learning from the research study. The early stage of perpendicular recording was conducted with the research philosophy of complementarity between perpendicular and horizontal recordings. Although present production of the perpendicular recording HDDs exceeds 600 million per year, development of perpendicular recording experienced the valley of death in the 1990s. The difficult period was overcome by the collaboration system of industrial and academic communities. The research on perpendicular recording brought about development of new research model as well as the historical view of the development of technology and innovation. The huge influence of perpendicular recording on society also taught us the relationship between science and technology with culture and civilization. - Research Highlights: > Discovery of circular magnetization led to idea of perpendicular recording. > SPT head and Co-Cr media were realized for practical perpendicular recording. > The complementarity between perpendicular and in-plane recording helped progress. > Death valley of research has been overcome by cooperation with potent companies. > Present mass production of HDDs is making a new civilization of the society.

  19. Plasma sheet pressure anisotropies

    International Nuclear Information System (INIS)

    Stiles, G.S.; Hones, E.W. Jr; Bame, S.J.; Asbridge, J.R.

    1978-01-01

    The ecliptic plane components of the pressure tensors for low-energy ( or =1.2 approximately 25% of the time. Due to the low energy density of the electrons, however, this anisotropy is not itself sufficient to balance the tension of the magnetic field

  20. CMB anisotropies interpolation

    NARCIS (Netherlands)

    Zinger, S.; Delabrouille, Jacques; Roux, Michel; Maitre, Henri

    2010-01-01

    We consider the problem of the interpolation of irregularly spaced spatial data, applied to observation of Cosmic Microwave Background (CMB) anisotropies. The well-known interpolation methods and kriging are compared to the binning method which serves as a reference approach. We analyse kriging

  1. 3D Anisotropy of Solar Wind Turbulence, Tubes, or Ribbons?

    Science.gov (United States)

    Verdini, Andrea; Grappin, Roland; Alexandrova, Olga; Lion, Sonny

    2018-01-01

    We study the anisotropy with respect to the local magnetic field of turbulent magnetic fluctuations at magnetofluid scales in the solar wind. Previous measurements in the fast solar wind obtained axisymmetric anisotropy, despite that the analysis method allows nonaxisymmetric structures. These results are probably contaminated by the wind expansion that introduces another symmetry axis, namely, the radial direction, as indicated by recent numerical simulations. These simulations also show that while the expansion is strong, the principal fluctuations are in the plane perpendicular to the radial direction. Using this property, we separate 11 yr of Wind spacecraft data into two subsets characterized by strong and weak expansion and determine the corresponding turbulence anisotropy. Under strong expansion, the small-scale anisotropy is consistent with the Goldreich & Sridhar critical balance. As in previous works, when the radial symmetry axis is not eliminated, the turbulent structures are field-aligned tubes. Under weak expansion, we find 3D anisotropy predicted by the Boldyrev model, that is, turbulent structures are ribbons and not tubes. However, the very basis of the Boldyrev phenomenology, namely, a cross-helicity increasing at small scales, is not observed in the solar wind: the origin of the ribbon formation is unknown.

  2. Enhanced post-annealing stability of perpendicular Ta/CoFeB/Mg/MgO multilayers by inhibiting Ta diffusion

    International Nuclear Information System (INIS)

    Li, Xu-Jing; Jiang, Shao-Long; Zhang, Jing-Yan; Liu, Qian-Qian; Liu, Yi-Wei; Zhao, Jian-Cheng; Wu, Zheng-Long; Feng, Chun; Li, Ming-Hua; Yu, Guang-Hua

    2016-01-01

    Graphical abstract: To reveal the underlying mechanism of Mg influence on the enhanced post-annealing stability of perpendicular Ta/CoFeB/Mg/MgO multilayers, the X-ray photoelectron spectroscopy analysis have been performed. It is found that a certain amount of Mg interlayer at the CoFeB/MgO interface could prevent the Ta oxidation to some extent due to the oxygen deficit MgO_x (x < 1), and consequently lower the diffusion motivation of Ta from the bottom layer to the CoFeB/MgO interfaces to some extent during the annealing process. The prevention of Ta diffusion realizes the effective hybridization of Fe and O at the CoFeB/MgO interface and maintains interfacial magnetic anisotropy (K_C_o_F_e_B_/_M_g_O). As a result, the perpendicular magnetic anisotropy at high annealing temperatures was maintained. - Highlights: • High annealing stability of perpendicular Ta/CoFeB/Mg/MgO multilayers was realized. • X-ray photoelectron spectroscopy analysis has been performed to explore the reasons. • The prevention of Ta diffusion was realized by introducing Mg at the CoFeB/MgO interface. - Abstracts: To reveal the underlying mechanism of Mg influence on the enhanced post-annealing stability of perpendicular Ta/CoFeB/Mg/MgO multilayers, the X-ray photoelectron spectroscopy analysis has been performed. It is found that a certain amount of Mg interlayer at the CoFeB/MgO interface could prevent the Ta oxidation, and consequently lower the diffusion motivation of Ta from the bottom layer to the CoFeB/MgO interfaces to some extent in the annealing process. The prevention of Ta diffusion realizes the effective hybridization of Fe and O at the CoFeB/MgO interface and maintains interfacial magnetic anisotropy (KCoFeB/MgO). As a result, the perpendicular magnetic anisotropy at high annealing temperatures is maintained

  3. Enhanced post-annealing stability of perpendicular Ta/CoFeB/Mg/MgO multilayers by inhibiting Ta diffusion

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xu-Jing; Jiang, Shao-Long; Zhang, Jing-Yan; Liu, Qian-Qian; Liu, Yi-Wei; Zhao, Jian-Cheng [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China); Wu, Zheng-Long [Analytical and Testing Center, Beijing Normal University, Beijing 100875 (China); Feng, Chun, E-mail: fengchun@ustb.edu.cn [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China); Li, Ming-Hua [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China); Yu, Guang-Hua, E-mail: ghyu@mater.ustb.edu.cn [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China)

    2016-03-01

    Graphical abstract: To reveal the underlying mechanism of Mg influence on the enhanced post-annealing stability of perpendicular Ta/CoFeB/Mg/MgO multilayers, the X-ray photoelectron spectroscopy analysis have been performed. It is found that a certain amount of Mg interlayer at the CoFeB/MgO interface could prevent the Ta oxidation to some extent due to the oxygen deficit MgO{sub x} (x < 1), and consequently lower the diffusion motivation of Ta from the bottom layer to the CoFeB/MgO interfaces to some extent during the annealing process. The prevention of Ta diffusion realizes the effective hybridization of Fe and O at the CoFeB/MgO interface and maintains interfacial magnetic anisotropy (K{sub CoFeB/MgO}). As a result, the perpendicular magnetic anisotropy at high annealing temperatures was maintained. - Highlights: • High annealing stability of perpendicular Ta/CoFeB/Mg/MgO multilayers was realized. • X-ray photoelectron spectroscopy analysis has been performed to explore the reasons. • The prevention of Ta diffusion was realized by introducing Mg at the CoFeB/MgO interface. - Abstracts: To reveal the underlying mechanism of Mg influence on the enhanced post-annealing stability of perpendicular Ta/CoFeB/Mg/MgO multilayers, the X-ray photoelectron spectroscopy analysis has been performed. It is found that a certain amount of Mg interlayer at the CoFeB/MgO interface could prevent the Ta oxidation, and consequently lower the diffusion motivation of Ta from the bottom layer to the CoFeB/MgO interfaces to some extent in the annealing process. The prevention of Ta diffusion realizes the effective hybridization of Fe and O at the CoFeB/MgO interface and maintains interfacial magnetic anisotropy (KCoFeB/MgO). As a result, the perpendicular magnetic anisotropy at high annealing temperatures is maintained.

  4. Study of anisotropy, magnetization reversal and damping in ultrathin Co films on MgO (0 0 1) substrate

    Science.gov (United States)

    Mallik, Srijani; Bedanta, Subhankar

    2018-01-01

    Ultrathin Co films of 3 nm thickness have been prepared on MgO (0 0 1) substrate in presence or absence of substrate pre-annealing. Uniaxial anisotropy is induced in the samples due to the deposition under oblique angle of incidence. Along with the oblique deposition induced anisotropy, another uniaxial anisotropy contribution has been observed due to pre-annealing. However, no cubic anisotropy has been observed here as compared to the thicker films. Angle dependent ferromagnetic resonance (FMR) measurement confirms the presence of two anisotropies in the pre-annealed sample with ∼18° misalignment with each other. The two anisotropy constants were calculated from both superconducting quantum interference device (SQUID) magnetometry and FMR spectroscopy. The magnetization reversal is governed by nucleation dominated aftereffect followed by domain wall motion for the pre-annealed sample. Branched domains are observed for the sample prepared without pre-annealing which indicates grain disorientation of Co. However, in the thicker (25 nm) Co films ripple domains were observed in contrary to ultrathin (3 nm) films.

  5. Exchange coupling in hybrid anisotropy magnetic multilayers quantified by vector magnetometry

    Energy Technology Data Exchange (ETDEWEB)

    Morrison, C., E-mail: C.Morrison.2@warwick.ac.uk; Miles, J. J.; Thomson, T. [School of Computer Science, University of Manchester, Manchester M13 9PL (United Kingdom); Anh Nguyen, T. N. [Materials Physics, School of ICT, KTH Royal Institute of Technology, Electrum 229, 164 40 Kista (Sweden); Spintronics Research Group, Laboratory for Nanotechnology (LNT), VNU-HCM, Ho Chi Minh City (Viet Nam); Fang, Y.; Dumas, R. K. [Department of Physics, University of Gothenburg, 412 96 Gothenburg (Sweden); Åkerman, J. [Materials Physics, School of ICT, KTH Royal Institute of Technology, Electrum 229, 164 40 Kista (Sweden); Department of Physics, University of Gothenburg, 412 96 Gothenburg (Sweden)

    2015-05-07

    Hybrid anisotropy thin film heterostructures, where layers with perpendicular and in-plane anisotropy are separated by a thin spacer, are novel materials for zero/low field spin torque oscillators and bit patterned media. Here, we report on magnetization reversal and exchange coupling in a archetypal Co/Pd (perpendicular)-NiFe (in-plane) hybrid anisotropy system studied using vector vibrating sample magnetometry. This technique allows us to quantify the magnetization reversal in each individual magnetic layer, and measure of the interlayer exchange as a function of non-magnetic spacer thickness. At large (>1 nm) spacer thicknesses Ruderman-Kittel-Kasuya-Yosida-like exchange dominates, with orange-peel coupling providing a significant contribution only for sub-nm spacer thickness.

  6. Electronic processes in uniaxially stressed p-type germanium

    Energy Technology Data Exchange (ETDEWEB)

    Dubon, Jr., Oscar Danilo [Univ. of California, Berkeley, CA (United States)

    1996-02-01

    Effect of uniaxial stress on acceptor-related electronic processes in Ge single crystals doped with Ga, Be, and Cu were studied by Hall and photo-Hall effect measurements in conjunction with infrared spectroscopy. Stress dependence of hole lifetime in p-type Ge single crystals is used as a test for competing models of non-radiative capture of holes by acceptors. Photo-Hall effect shows that hole lifetime in Ga- and Be-doped Ge increases by over one order of magnitude with uniaxial stress at liq. He temps. Photo-Hall of Ge:Be shows a stress-induced change in the temperature dependence of hole lifetime. This is consistent with observed increase of responsivity of Ge:Ga detectors with uniaxial stress. Electronic properties of Ge:Cu are shown to change dramatically with uniaxial stress; the results provide a first explanation for the performance of uniaxially stressed, Cu-diffused Ge:Ga detectors which display a high conductivity in absence of photon signal and therefore have poor sensitivity.

  7. Texture and anisotropy analysis of Qusaiba shales

    KAUST Repository

    Kanitpanyacharoen, Waruntorn

    2011-02-17

    Scanning and transmission electron microscopy, synchrotron X-ray diffraction, microtomography and ultrasonic velocity measurements were used to characterize microstructures and anisotropy of three deeply buried Qusaiba shales from the Rub\\'al-Khali basin, Saudi Arabia. Kaolinite, illite-smectite, illite-mica and chlorite show strong preferred orientation with (001) pole figure maxima perpendicular to the bedding plane ranging from 2.4-6.8 multiples of a random distribution (m.r.d.). Quartz, feldspars and pyrite crystals have a random orientation distribution. Elastic properties of the polyphase aggregate are calculated by averaging the single crystal elastic properties over the orientation distribution, assuming a nonporous material. The average calculated bulk P-wave velocities are 6.2 km/s (maximum) and 5.5 km/s (minimum), resulting in a P-wave anisotropy of 12%. The calculated velocities are compared with those determined from ultrasonic velocity measurements on a similar sample. In the ultrasonic experiment, which measures the effects of the shale matrix as well as the effects of porosity, velocities are smaller (P-wave maximum 5.3 km/s and minimum 4.1 km/s). The difference between calculated and measured velocities is attributed to the effects of anisotropic pore structure and to microfractures present in the sample, which have not been taken into account in the matrix averaging. © 2011 European Association of Geoscientists & Engineers.

  8. Elastic Anisotropy of Basalt

    Science.gov (United States)

    Becker, K.; Shapiro, S.; Stanchits, S.; Dresen, G.; Kaselow, A.; Vinciguerra, S.

    2005-12-01

    Elastic properties of rocks are sensitive to changes of the in-situ stress and damage state. In particular, seismic velocities are strongly affected by stress-induced formation and deformation of cracks or shear-enhanced pore collapse. The effect of stress on seismic velocities as a result of pore space deformation in isotropic rock at isostatic compression may be expressed by the equation: A+K*P-B*exp (-D*P) (1), where P=Pc-Pp is the effective pressure, the pure difference between confining pressure and pore pressure. The parameter A, K, B and D describe material constants determined using experimental data. The physical meaning of the parameters is given by Shapiro (2003, in Geophysics Vol.68(Nr.2)). Parameter D is related to the stress sensitivity of the rock. A similar relation was derived by Shapiro and Kaselow (2005, in Geophysics in press) for weak anisotropic rocks under arbitrary load. They describe the stress dependent anisotropy in terms of Thomson's (1986, in Geophysics, Vol. 51(Nr.10)) anisotropy parameters ɛ and γ as a function of stress in the case of an initially isotropic rock: ɛ ∝ E2-E3, γ ∝ E3-E2 (2) with Ei=exp (D*Pi). The exponential terms Ei are controlled by the effective stress components Pi. To test this relation, we have conducted a series of triaxial compression tests on dry samples of initially isotropic Etnean Basalt in a servo-controlled MTS loading frame equipped with a pressure cell. Confining pressure was 60, 40 and 20 MPa. Samples were 5 cm in diameter and 10 cm in length. Elastic anisotropy was induced by axial compression of the samples through opening and growth of microcracks predominantly oriented parallel to the sample axis. Ultrasonic P- and S- wave velocities were monitored parallel and normal to the sample axis by an array of 20 piezoceramic transducers glued to the surface. Preamplified full waveform signals were stored in two 12 channel transient recorders. According to equation 2 the anisotropy parameters are

  9. Solar Wind Proton Temperature Anisotropy: Linear Theory and WIND/SWE Observations

    Science.gov (United States)

    Hellinger, P.; Travnicek, P.; Kasper, J. C.; Lazarus, A. J.

    2006-01-01

    We present a comparison between WIND/SWE observations (Kasper et al., 2006) of beta parallel to p and T perpendicular to p/T parallel to p (where beta parallel to p is the proton parallel beta and T perpendicular to p and T parallel to p are the perpendicular and parallel proton are the perpendicular and parallel proton temperatures, respectively; here parallel and perpendicular indicate directions with respect to the ambient magnetic field) and predictions of the Vlasov linear theory. In the slow solar wind, the observed proton temperature anisotropy seems to be constrained by oblique instabilities, by the mirror one and the oblique fire hose, contrary to the results of the linear theory which predicts a dominance of the proton cyclotron instability and the parallel fire hose. The fast solar wind core protons exhibit an anticorrelation between beta parallel to c and T perpendicular to c/T parallel to c (where beta parallel to c is the core proton parallel beta and T perpendicular to c and T parallel to c are the perpendicular and parallel core proton temperatures, respectively) similar to that observed in the HELIOS data (Marsch et al., 2004).

  10. Controlling the competing magnetic anisotropy energies in FineMET amorphous thin films with ultra-soft magnetic properties

    Directory of Open Access Journals (Sweden)

    Ansar Masood

    2017-05-01

    Full Text Available Thickness dependent competing magnetic anisotropy energies were investigated to explore the global magnetic behaviours of FineMET amorphous thin films. A dominant perpendicular magnetization component in the as-deposited state of thinner films was observed due to high magnetoelastic anisotropy energy which arises from stresses induced at the substrate-film interface. This perpendicular magnetization component decreases with increasing film thickness. Thermal annealing at elevated temperature revealed a significant influence on the magnetization state of the FineMET thin films and controlled annealing steps leads to ultra-soft magnetic properties, making these thin films alloys ideal for a wide range of applications.

  11. Some device implications of voltage controlled magnetic anisotropy in Co/Gd2O3 thin films through REDOX chemistry

    Science.gov (United States)

    Hao, Guanhua; Noviasky, Nicholas; Cao, Shi; Sabirianov, Ildar; Yin, Yuewei; Ilie, Carolina C.; Kirianov, Eugene; Sharma, Nishtha; Sokolov, Andrei; Marshall, Andrew; Xu, Xiaoshan; Dowben, Peter A.

    2018-04-01

    The effect of intermediate interfacial oxidation on the in-plane magnetization of multilayer stack Pt/Co/Gd2O3, on a p-type silicon substrate, has been investigated by magneto-optical Kerr effect (MOKE) measurements, the anomalous Hall effect, and magnetoresistance measurements. While voltage controlled perpendicular magnetic anisotropy of a metal/oxide heterostructure is known, this heterostructure displays an inverse relationship between voltage and coercivity. The anomalous Hall effect demonstrates a significant change in hysteresis, with the applied bias sign. There is a higher perpendicular magnetic anisotropy with positive bias exposure.

  12. Uniaxial Tension Test of Slender Reinforced Early Age Concrete Members

    Directory of Open Access Journals (Sweden)

    Wenbo Zhang

    2011-08-01

    Full Text Available The present study aims to obtain the tensile properties of early age concrete based on a uniaxial tension test employing RC slender members. First, the paper shows that concrete strain is equal to the strain of rebar at the mid-span of the RC member. The tensile Young’s modulus and the strain capacity of early age concrete are estimated using strain measurements. The experiment indicated that the tensile Young’s modulus at an early age is higher than the compressive modulus. This observation was similar to one found in a previous investigation which used a direct tension test of early age concrete. Moreover, the paper describes how an empirical equation for mature concrete can be applied to the relation between uniaxial tensile strength and splitting tensile strength even in early age concrete. Based on a uniaxial tension test, the paper proposes an empirical equation for the relationship between standard bond stresses and relative slip.

  13. Elastic properties of uniaxial-fiber reinforced composites - General features

    Science.gov (United States)

    Datta, Subhendu; Ledbetter, Hassel; Lei, Ming

    The salient features of the elastic properties of uniaxial-fiber-reinforced composites are examined by considering the complete set of elastic constants of composites comprising isotropic uniaxial fibers in an isotropic matrix. Such materials exhibit transverse-isotropic symmetry and five independent elastic constants in Voigt notation: C(11), C(33), C(44), C(66), and C(13). These C(ij) constants are calculated over the entire fiber-volume-fraction range 0.0-1.0, using a scattered-plane-wave ensemple-average model. Some practical elastic constants such as the principal Young moduli and the principal Poisson ratios are considered, and the behavior of these constants is discussed. Also presented are the results for the four principal sound velocities used to study uniaxial-fiber-reinforced composites: v(11), v(33), v(12), and v(13).

  14. Quarkonium dissociation by anisotropy

    Science.gov (United States)

    Chernicoff, Mariano; Fernández, Daniel; Mateos, David; Trancanelli, Diego

    2013-01-01

    We compute the screening length for quarkonium mesons moving through an anisotropic, strongly coupled mathcal{N} = 4 super Yang-Mills plasma by means of its gravity dual. We present the results for arbitrary velocities and orientations of the mesons, as well as for arbitrary values of the anisotropy. The anisotropic screening length can be larger or smaller than the isotropic one, and this depends on whether the comparison is made at equal temperatures or at equal entropy densities. For generic motion we find that: (i) mesons dissociate above a certain critical value of the anisotropy, even at zero temperature; (ii) there is a limiting velocity for mesons in the plasma, even at zero temperature; (iii) in the ultra-relativistic limit the screening length scales as (1 - v 2)ɛ with ɛ = 1 /2, in contrast with the isotropic result ɛ = 1 /4.

  15. Supernovae anisotropy power spectrum

    Energy Technology Data Exchange (ETDEWEB)

    Ghodsi, Hoda; Baghram, Shant [Department of Physics, Sharif University of Technology, P.O. Box 11155-9161, Tehran (Iran, Islamic Republic of); Habibi, Farhang, E-mail: h.ghodsi@mehr.sharif.ir, E-mail: baghram@sharif.edu, E-mail: habibi@lal.in2p3.fr [LAL-IN2P3/CNRS, BP 34, 91898 Orsay Cedex (France)

    2017-10-01

    We contribute another anisotropy study to this field of research using Type Ia supernovae (SNe Ia). In this work, we utilise the power spectrum calculation method and apply it to both the current SNe Ia data and simulation. Using the Union2.1 data set at all redshifts, we compare the spectrum of the residuals of the observed distance moduli to that expected from an isotropic universe affected by the Union2.1 observational uncertainties at low multipoles. Through this comparison we find a dipolar anisotropy with tension of less that 2σ towards l = 171° ± 21° and b = −26° ± 28° which is mainly induced by anisotropic spatial distribution of the SNe with z > 0.2 rather than being a cosmic effect. Furthermore, we find a tension of ∼ 4σ at ℓ = 4 between the two spectra. Our simulations are constructed with the characteristics of the upcoming surveys like the Large Synoptic Survey Telescope (LSST), which shall bring us the largest SNe Ia collection to date. We make predictions for the amplitude of a possible dipolar anisotropy that would be detectable by future SNe Ia surveys.

  16. Three-dimensional spin mapping of antiferromagnetic nanopyramids having spatially alternating surface anisotropy at room temperature.

    Science.gov (United States)

    Wang, Kangkang; Smith, Arthur R

    2012-11-14

    Antiferromagnets play a key role in modern spintronic devices owing to their ability to modify the switching behavior of adjacent ferromagnets via the exchange bias effect. Consequently, detailed measurements of the spin structure at antiferromagnetic interfaces and surfaces are highly desirable, not only for advancing technologies but also for enabling new insights into the underlying physics. Here using spin-polarized scanning tunneling microscopy at room-temperature, we reveal in three-dimensions an orthogonal spin structure on antiferromagnetic compound nanopyramids. Contrary to expected uniaxial anisotropy based on bulk properties, the atomic terraces are found to have alternating in-plane and out-of-plane magnetic anisotropies. The observed layer-wise alternation in anisotropy could have strong influences on future nanoscale spintronic applications.

  17. A vector model for off-axis hysteresis loops using anisotropy field

    International Nuclear Information System (INIS)

    Jamali, Ali; Torre, Edward Della; Cardelli, Ermanno; ElBidweihy, Hatem; Bennett, Lawrence H.

    2016-01-01

    A model for the off-axis vector magnetization of a distribution of uniaxial particles is presented. Recent work by the authors decomposed the magnetization into two components and modeled the total vector magnetization as their vector sum. In this paper, to account for anisotropy, the direction of the reversible magnetization component is specified by the vector sum of the applied field and an effective anisotropy field. The formulation of the new anisotropy field (AF) model is derived and its results are discussed considering (i) oscillation and rotational modes, (ii) lag angle, and (iii) unitary magnetization. The advantages of the AF model are outlined by comparing its results to the results of the classical Stoner–Wohlfarth model.

  18. A vector model for off-axis hysteresis loops using anisotropy field

    Energy Technology Data Exchange (ETDEWEB)

    Jamali, Ali, E-mail: alijamal@gwu.edu [Electrical and Computer Engineering Department, The George Washington University, Washington, D.C. 20052 (United States); Torre, Edward Della [Electrical and Computer Engineering Department, The George Washington University, Washington, D.C. 20052 (United States); Cardelli, Ermanno [Department of Engineering, University of Perugia, Perugia (Italy); ElBidweihy, Hatem [Electrical and Computer Engineering Department, United States Naval Academy, Annapolis, MD 21402 (United States); Bennett, Lawrence H. [Electrical and Computer Engineering Department, The George Washington University, Washington, D.C. 20052 (United States)

    2016-11-15

    A model for the off-axis vector magnetization of a distribution of uniaxial particles is presented. Recent work by the authors decomposed the magnetization into two components and modeled the total vector magnetization as their vector sum. In this paper, to account for anisotropy, the direction of the reversible magnetization component is specified by the vector sum of the applied field and an effective anisotropy field. The formulation of the new anisotropy field (AF) model is derived and its results are discussed considering (i) oscillation and rotational modes, (ii) lag angle, and (iii) unitary magnetization. The advantages of the AF model are outlined by comparing its results to the results of the classical Stoner–Wohlfarth model.

  19. Strain-dependent magnetic anisotropy in GaMnAs on InGaAs templates

    Energy Technology Data Exchange (ETDEWEB)

    Daeubler, Joachim; Glunk, Michael; Schwaiger, Stephan; Dreher, Lukas; Schoch, Wladimir; Sauer, Rolf; Limmer, Wolfgang [Institut fuer Halbleiterphysik, Universitaet Ulm, 89069 Ulm (Germany)

    2008-07-01

    We have systematically studied the influence of strain on the magnetic anisotropy of GaMnAs by means of HRXRD reciprocal space mapping and angle-dependent magnetotransport. For this purpose, a series of GaMnAs layers with Mn contents of {proportional_to}5% was grown by low-temperature MBE on relaxed InGaAs/GaAs templates with different In concentrations, enabling us to vary the strain in the GaMnAs layers continuously from tensile to compressive, including the unstrained state. Considering both, as-grown and annealed samples, the anisotropy parameter describing the uniaxial out-of-plane magnetic anisotropy has been found to vary linearly with hole density and strain. As a consequence, the out-of-plane direction gradually undergoes a transition from a magnetic hard axis to a magnetic easy axis from compressive to tensile strain.

  20. RAPID COSMIC-RAY ACCELERATION AT PERPENDICULAR SHOCKS IN SUPERNOVA REMNANTS

    Energy Technology Data Exchange (ETDEWEB)

    Takamoto, Makoto; Kirk, John G., E-mail: mtakamoto@eps.s.u-tokyo.ac.jp, E-mail: john.kirk@mpi-hd.mpg.de [Max-Planck-Institut für Kernphysik, Postfach 103980, D-69029 Heidelberg (Germany)

    2015-08-10

    Perpendicular shocks are shown to be rapid particle accelerators that perform optimally when the ratio u{sub s} of the shock speed to the particle speed roughly equals the ratio 1/η of the scattering rate to the gyro frequency. We use analytical methods and Monte-Carlo simulations to solve the kinetic equation that governs the anisotropy generated at these shocks, and find, for ηu{sub s} ≈ 1, that the spectral index softens by unity and the acceleration time increases by a factor of two compared to the standard result of the diffusive shock acceleration theory. These results provide a theoretical basis for the 30 year old conjecture that a supernova exploding into the wind of a Wolf–Rayet star may accelerate protons to an energy exceeding 10{sup 15} eV.

  1. Stability analysis of perpendicular magnetic trilayers with a field-like spin torque

    International Nuclear Information System (INIS)

    Wang, Ri-Xing; Zhao, Jing-Li; He, Peng-Bin; Gu, Guan-Nan; Li, Zai-Dong; Pan, An-Lian; Liu, Quan-Hui

    2013-01-01

    We have analytically studied the magnetization dynamics in magnetic trilayers with perpendicular anisotropy for both free and pinned layers. By linear stability analysis, we obtain the phase diagram parameterized by the current, magnetic field and relative strength of the field-like spin torque to Slonczewski torque. Under the control of the current and external magnetic field, several magnetic states, such as quasi-parallel and quasi-antiparallel stable states, out-of-plane precession, and bistable states can be realized. The precession frequency can be expressed as a function of the current and external magnetic field. In addition, the presence of field-like spin torque can change the switching current and precession frequency. - Highlights: ► The phase diagram is obtained by linear stability analysis. ► The precession frequency can be controlled by the current and magnetic field. ► Field-like spin torque can change instability current and precession frequency.

  2. Role of an ultrathin platinum seed layer in antiferromagnet-based perpendicular exchange coupling and its electrical manipulation

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Y.Y., E-mail: wangyy@buaa.edu.cn [Department of Physics, Beihang University, Beijing 100191 (China); Key Laboratory of Advanced Materials (MOE), School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Song, C., E-mail: songcheng@mail.tsinghua.edu.cn [Key Laboratory of Advanced Materials (MOE), School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Zhang, J.Y. [Department of Physics, Beihang University, Beijing 100191 (China); Pan, F. [Key Laboratory of Advanced Materials (MOE), School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China)

    2017-04-15

    The requirement for low-power consumption advances the development of antiferromagnetic (AFM) spintronics manipulated by electric fields. Here we report an electrical manipulation of metallic AFM moments within IrMn/[Co/Pt] by interface engineering, where ultrathin non-magnetic metals are highlighted between IrMn and ferroelectric substrates. Ultrathin Pt seed layers are proved to be vital in elevating the blocking temperature and enhancing the perpendicular exchange coupling through modulating the domain structures of as-prepared IrMn AFM. Further electrical manipulations of perpendicular magnetic anisotropy crucially verify the indispensable role of pre-deposited ultrathin Pt layers in modulating IrMn antiferromagnetic moments, which is confirmed by the intimate correlation between the electrically manipulating AFM and improving its blocking temperature. Instead of immediate contact between IrMn AFM and ferroelectric substrates in a conventional way, interface engineering by adopting ultrathin seed layers here adds a new twist to the electrical modulation of AFM metals. This would provide scientific basis on how to manipulate AFM moments and optimize the design of practical AFM spintronics. - Highlights: • An alternative for manipulating antiferromagnet by interface engineering is provided. • Ultrathin Pt seed layers are vital in elevating the blocking temperature of IrMn. • Perpendicular exchange coupling in IrMn/[Co/Pt] can be modulated by seed layers. • Ultrathin Pt seed layers enable electrical control of perpendicular exchange coupling.

  3. Role of an ultrathin platinum seed layer in antiferromagnet-based perpendicular exchange coupling and its electrical manipulation

    International Nuclear Information System (INIS)

    Wang, Y.Y.; Song, C.; Zhang, J.Y.; Pan, F.

    2017-01-01

    The requirement for low-power consumption advances the development of antiferromagnetic (AFM) spintronics manipulated by electric fields. Here we report an electrical manipulation of metallic AFM moments within IrMn/[Co/Pt] by interface engineering, where ultrathin non-magnetic metals are highlighted between IrMn and ferroelectric substrates. Ultrathin Pt seed layers are proved to be vital in elevating the blocking temperature and enhancing the perpendicular exchange coupling through modulating the domain structures of as-prepared IrMn AFM. Further electrical manipulations of perpendicular magnetic anisotropy crucially verify the indispensable role of pre-deposited ultrathin Pt layers in modulating IrMn antiferromagnetic moments, which is confirmed by the intimate correlation between the electrically manipulating AFM and improving its blocking temperature. Instead of immediate contact between IrMn AFM and ferroelectric substrates in a conventional way, interface engineering by adopting ultrathin seed layers here adds a new twist to the electrical modulation of AFM metals. This would provide scientific basis on how to manipulate AFM moments and optimize the design of practical AFM spintronics. - Highlights: • An alternative for manipulating antiferromagnet by interface engineering is provided. • Ultrathin Pt seed layers are vital in elevating the blocking temperature of IrMn. • Perpendicular exchange coupling in IrMn/[Co/Pt] can be modulated by seed layers. • Ultrathin Pt seed layers enable electrical control of perpendicular exchange coupling.

  4. Temperature dependence of the interfacial magnetic anisotropy in W/CoFeB/MgO

    Directory of Open Access Journals (Sweden)

    Kyoung-Min Lee

    2017-06-01

    Full Text Available The interfacial perpendicular magnetic anisotropy in W/CoFeB (1.2 ∼ 3 nm/MgO thin film structures is strongly dependent on temperature, and is significantly reduced at high temperature. The interfacial magnetic anisotropy is generally proportional to the third power of magnetization, but an additional factor due to thermal expansion is required to explain the temperature dependence of the magnetic anisotropy of ultrathin CoFeB films. The reduction of the magnetic anisotropy is more prominent for the thinner films; as the temperature increases from 300 K to 400 K, the anisotropy is reduced ∼50% for the 1.2-nm-thick CoFeB, whereas the anisotropy is reduced ∼30% for the 1.7-nm-thick CoFeB. Such a substantial reduction of magnetic anisotropy at high temperature is problematic for data retention when incorporating W/CoFeB/MgO thin film structures into magneto-resistive random access memory devices. Alternative magnetic materials and structures are required to maintain large magnetic anisotropy at elevated temperatures.

  5. Gaps, tears and seismic anisotropy around the subducting slabs of the Antilles

    Science.gov (United States)

    Schlaphorst, David; Kendall, J.-Michael; Baptie, Brian; Latchman, Joan L.; Tait, Steve

    2017-02-01

    Seismic anisotropy in and beneath the subducting slabs of the Antilles is investigated using observations of shear-wave splitting. We use a combination of teleseismic and local events recorded at three-component broadband seismic stations on every major island in the area to map anisotropy in the crust, the mantle wedge and the slab/sub-slab mantle. To date this is the most comprehensive study of anisotropy in this region, involving 52 stations from 8 seismic networks. Local event delay times (0.21 ± 0.12 s) do not increase with depth, indicating a crustal origin in anisotropy and an isotropic mantle wedge. Teleseismic delay times are much larger (1.34 ± 0.47 s), with fast shear-wave polarisations that are predominantly parallel to trend of the arc. These observations can be interpreted three ways: (1) the presence of pre-existing anisotropy in the subducting slab; (2) anisotropy due to sub-slab mantle flow around the eastern margin of the nearly stationary Caribbean plate; (3) some combination of both mechanisms. However, there are two notable variations in the trench-parallel pattern of anisotropy - trench-perpendicular alignment is observed in narrow regions east of Puerto Rico and south of Martinique. These observations support previously proposed ideas of eastward sublithospheric mantle flow through gaps in the slab. Furthermore, the pattern of anisotropy south of Martinique, near Saint Lucia is consistent with a previously proposed location for the boundary between the North and South American plates.

  6. Magnetization switching diagram of a perpendicular synthetic ferrimagnet CoFeB/Ta/CoFeB bilayer

    Energy Technology Data Exchange (ETDEWEB)

    Koplak, O. [Immanuel Kant Baltic Federal University, 236041 Kaliningrad (Russian Federation); Institute of Problems of Chemical Physics, 142432 Chernogolovka, Moscow (Russian Federation); Talantsev, A. [Institute of Problems of Chemical Physics, 142432 Chernogolovka, Moscow (Russian Federation); Lu, Y.; Hamadeh, A.; Pirro, P.; Hauet, T. [Institut Jean Lamour, UMR 7198 CNRS, Université de Lorraine (France); Morgunov, R., E-mail: morgunov2005@yandex.ru [Institute of Problems of Chemical Physics, 142432 Chernogolovka, Moscow (Russian Federation); Tambov State Technical University, 392000 Tambov (Russian Federation); Mangin, S. [Institut Jean Lamour, UMR 7198 CNRS, Université de Lorraine (France)

    2017-07-01

    Highlights: • Anisotropy, Zeeman and exchange energy determine sequence of magnetic transitions. • Three temperature ranges manifest different shapes of the hysteresis loop. • The critical transition fields are temperature dependent. - Abstract: Magnetic configurations in synthetic ferrimagnet CoFeB/Ta/CoFeB bilayer with strong perpendicular anisotropy have been systematically studied. Magnetization versus field hysteresis loop has been measured for different temperature ranging from 5 to 300 K. The applied field – temperature (H-T) magnetization switching diagram has been constructed by extracting the different switching fields as a function of temperature. This switching diagram can be well explained by considering the competition between energy barrier of layer’s magnetization reversal, interlayer exchange coupling, and Zeeman energy.

  7. Magnetization switching diagram of a perpendicular synthetic ferrimagnet CoFeB/Ta/CoFeB bilayer

    International Nuclear Information System (INIS)

    Koplak, O.; Talantsev, A.; Lu, Y.; Hamadeh, A.; Pirro, P.; Hauet, T.; Morgunov, R.; Mangin, S.

    2017-01-01

    Highlights: • Anisotropy, Zeeman and exchange energy determine sequence of magnetic transitions. • Three temperature ranges manifest different shapes of the hysteresis loop. • The critical transition fields are temperature dependent. - Abstract: Magnetic configurations in synthetic ferrimagnet CoFeB/Ta/CoFeB bilayer with strong perpendicular anisotropy have been systematically studied. Magnetization versus field hysteresis loop has been measured for different temperature ranging from 5 to 300 K. The applied field – temperature (H-T) magnetization switching diagram has been constructed by extracting the different switching fields as a function of temperature. This switching diagram can be well explained by considering the competition between energy barrier of layer’s magnetization reversal, interlayer exchange coupling, and Zeeman energy.

  8. Enhanced emission of high-energy photons perpendicular to the reaction plane in α+Th reactions

    International Nuclear Information System (INIS)

    Tegner, P.; Marianski, B.; Morsch, H.P.; Rogge, M.; Bargholtz, C.; Decowski, P.; Zemlo, L.

    1991-01-01

    High-energy photon and neutron emission has been measured in coincidence with fission fragments in α+ 232 Th reactions at 170 MeV. From measurements parallel and perpendicular to the fission plane, anisotropies relative to the reaction plane were determined. The in-plane/out-of-plane intensity ratio is 0.72(7) for photons with energies above 20 MeV and 11(3) for neutrons at 35 MeV. The result for high-energy photons can be explained by nucleon-nucleon bremsstrahlung if the initial flow of nucleons has a correlation to the reaction plane similar to the one observed for fast neutrons

  9. In-plane magnetic anisotropy and temperature dependence of switching field in (Ga, Mn) as ferromagnetic semiconductors.

    Science.gov (United States)

    Kamara, S; Terki, F; Dumas, R; Dehbaoui, M; Sadowski, J; Galéra, R M; Tran, Q-H; Charar, S

    2012-06-01

    We explore the magnetic anisotropy of GaMnAs ferromagnetic semiconductor by Planar Hall Effect (PHE) measurements. Using low magnitude of applied magnetic field (i.e., when the magnitude H is smaller than both cubic Hc and uniaxial Hu anisotropy field), we have observed various shapes of applied magnetic field direction dependence of Planar Hall Resistance (PHR). In particular, in two regions of temperature. At T Tc/2 the "zigzag-shape" signal of PHR. They reflect different magnetic anisotropy and provide information about magnetization reversal process in GaMnAs ferromagnetic semiconductor. The theoretical model calculation of PHR based on the free energy density reproduces well the experimental data. We report also the temperature dependence of anisotropy constants and magnetization orientations. The transition of easy axis from biaxial to uniaxiale axes has been observed and confirmed by SQUID measurements.

  10. Magnetic phase transitions and hydrostatic pressure or uniaxial stress experiments

    International Nuclear Information System (INIS)

    Bloch, D.

    1980-01-01

    Crystals submitted to high hydrostatic pressure or uniaxial stress have been investigated by means of neutron scattering. The techniques used are described and applications to pressure or stress induced T = 0 magnetic to nonmagnetic transitions (Pr,PrSb) and continuous to discontinuous order-disorder transitions (MnO) are given. (orig.)

  11. Functional possibilities of nonlinear crystals for frequency conversion: uniaxial crystals

    Energy Technology Data Exchange (ETDEWEB)

    Andreev, Yu M [Institute of Monitoring of Climatic and Ecological Systems, Siberian Branch of the Russian Academy of Sciences, Tomsk (Russian Federation); Arapov, Yu D; Kasyanov, I V [E.I. Zababakhin All-Russian Scientific-Research Institute of Technical Physics, Russian Federal Nuclear Centre, Snezhinsk, Chelyabinsk region (Russian Federation); Grechin, S G; Nikolaev, P P [N.E. Bauman Moscow State Technical University, Moscow (Russian Federation)

    2016-01-31

    The method and results of the analysis of phase-matching and nonlinear properties for all point groups of symmetry of uniaxial crystals that determine their functional possibilities for solving various problems of nonlinear frequency conversion of laser radiation are presented. (nonlinear optical phenomena)

  12. Technique for measurements of plane waves of uniaxial strain

    International Nuclear Information System (INIS)

    Graham, R.A.

    1977-01-01

    The measurement of plane waves in uniaxial strain, in which large surface areas are loaded and the measurements are restricted to a central region that is not influenced by lateral boundaries, is discussed. Measuring techniques are covered and instruments are discussed

  13. Chamber for uniaxial pressure application at low temperatures

    International Nuclear Information System (INIS)

    Grillo, M.L.N.; Carmo, L.C.S. do; Picon, A.P.

    1984-08-01

    A chamber for alignment of low temperature ferroelastic domains in crystals by the use of uniaxial stress was built. The system allows the use of EPR and optical techniques, as well as X-ray irradiation at temperatures as low as 77K. (Author) [pt

  14. Microwave holography in a uniaxial anial anisotropic plasma

    International Nuclear Information System (INIS)

    Nagai, Keinosuke; Suzuki, Michio

    1974-01-01

    Properties of a hologram constructed in a uniaxial anisotropic medium, namely in a gyro-plasma were investigated theoretically. We considered the interference patterns of ordinary waves and extraordinary waves from a source such as a hologram. An element of permitivity tensor can be measured by the reconstruction process from this hologram. (auth.)

  15. Effect of hexane treatment and uniaxial stretching on bending ...

    African Journals Online (AJOL)

    PVDF) film was studied. The quantity, β31, defined as the bending piezoelectric stress constant, was calculated. After hexane treatment and uniaxial stretching of the PVDF film, the value of β31 was 5.75 mV/m and 8.00 mV/m for draw ratio of ...

  16. Thickness dependence of the magnetic anisotropy and dynamic magnetic response of ferromagnetic NiFe films

    International Nuclear Information System (INIS)

    Silva, E F; Corrêa, M A; Chesman, C; Bohn, F; Della Pace, R D; Plá Cid, C C; Kern, P R; Carara, M; Alves Santos, O; Rodríguez-Suárez, R L; Azevedo, A; Rezende, S M

    2017-01-01

    We investigate the thickness dependence of the magnetic anisotropy and dynamic magnetic response of ferromagnetic NiFe films. We go beyond quasi-static measurements and focus on the dynamic magnetic response by considering three complementary techniques: the ferromagnetic resonance, magnetoimpedance and magnetic permeability measurements. We verify remarkable modifications in the magnetic anisotropy, i.e. the well-known behavior of in-plane uniaxial magnetic anisotropy systems gives place to a complex magnetic behavior as the thickness increases, and splits the films in two groups according to the magnetic properties. We identify magnetoimpedance and magnetic permeability curves with multiple resonance peaks, as well as the evolution of the ferromagnetic resonance absorption spectra, as fingerprints of strong changes of the magnetic properties associated to the vanishing of the in-plane magnetic anisotropy and to the emergence of non-homogeneous magnetization configuration, local anisotropies and out-of-plane anisotropy contribution arisen as a consequence of the non-uniformities of the stress stored in the film as the thickness is increased and/or to the columnar growth of the film. We interpret the experimental results in terms of the structural and morphological properties, quasi-static magnetic behavior, magnetic domain structure and different mechanisms governing the magnetization dynamics at distinct frequency ranges. (paper)

  17. Variation in the strain anisotropy of Zircaloy with temperature and strain

    International Nuclear Information System (INIS)

    Hindle, E.D.; Worswick, D.

    1984-04-01

    Strain anisotropy was investigated at temperatures in the range 293 to 1117K in circular tensile specimens prepared from rolled Zircaloy-2 plate so that their tensile axes were parallel to and transverse to the rolling direction. The strain anisotropy factor for both types of specimen increased markedly in the high alpha phase region above 923K reaching a maximum at circa 1070K. Above this temperature in the alpha-plus-beta phase region the strain anisotropy decreased rapidly as the proportion of beta phase increased and was almost non-existent at 1173K. The strain anisotropy was markedly strain dependent, particularly in the high alpha phase region. The study was extended to Zircaloy-4 pressurized water reactor (PWR) 17 x 17 type fuel rod tubing specimens which were strained under biaxial conditions using cooling conditions which promoted uniform diametral strain over most of their lengths (circa 250 mm). In these circumstances the strain anisotropy is manifest by a reduction in length. Measurement of this change along with that in diameter and wall thickness produced data from which the strain anisotropy factor was calculated. The results, although influenced by additional factors discussed in the paper, were similar to those observed in the uniaxial Zircaloy-2 tensile tests. (author)

  18. Strain-induced recovery of electronic anisotropy in 90°-twisted bilayer phosphorene

    Science.gov (United States)

    Xie, Jiafeng; Luo, Qiangjun; Jia, Lei; Zhang, Z. Y.; Shi, H. G.; Yang, D. Z.; Si, M. S.

    2018-01-01

    It is well known that anisotropy determines the preferred transport direction of carriers. To manipulate the anisotropy is an exciting topic in two-dimensional materials, where the carriers are confined within individual layers. In this work, it is found that uniaxial strain can tune the electronic anisotropy of the 90°-twisted bilayer phosphorene. In this unique bilayer structure, the zigzag direction of one layer corresponds to the armchair one of the other layer and vice versa. Owing to this complementary structure, the directional (zigzag or armchair) deformation response to strain of one layer is opposite to that of the other layer, where the in-plane positive Poisson's ratio plays a key role. As a result, the doubly degenerate highest valence bands split, followed by a recovery of anisotropy. More interestingly, such an anisotropy, namely, the ratio of the effective mass along the Γ \\text- X direction to that along the Γ \\text- Y direction, reaches as high as 6 under a small strain of 1%, and keeps nearly unchanged up to a strain of 3%. In addition, high anisotropy only holds for hole carriers as the conduction band is insensitive to strain. These findings should shed new light on the design of semiconducting devices, where the hole acts as the transport carrier.

  19. Magnetic anisotropy in GaMnAs; Magnetische Anisotropie in GaMnAs

    Energy Technology Data Exchange (ETDEWEB)

    Daeubler, Joachim

    2009-07-02

    The goal of the present work was the detailed investigation of the impact of parameters like vertical strain, hole concentration, substrate orientation and patterning on the MA in GaMnAs. At first a method is introduced enabling us to determine the MA from angle-dependent magnetotransport measurements. This method was used to analyze the impact of vertical strain {epsilon}{sub zz} on the MA in a series of GaMnAs layers with a Mn content of 5% grown on relaxed InGaAs-templates. While hole concentration and Curie temperature were found to be unaffected by vertical strain, a significant dependence of the MA on {epsilon}{sub zz} was found. The most pronounced dependence was observed for the anisotropy parameter B{sub 2} {sub perpendicular} {sub to}, representing the intrinsic contribution to the MA perpendicular to the layer plane. For this parameter a linear dependence on {epsilon}{sub zz} was found, resulting in a strain-induced transition of the magnetic easy axis with increasing strain from in-plane to out-of-plane at {epsilon}{sub zz} {approx} -0.13%. Post-growth annealing of the samples leads to an outdiffusion and/or regrouping of the highly mobile Mn interstitial donor defects, resulting in an increase in both p and T{sub C}. For the annealed samples, the transition from in-plane to out-of-plane easy axis takes place at {epsilon}{sub zz} {approx} -0.07%. From a comparison of as-grown and annealed samples, B{sub 2} {sub perpendicular} {sub to} was found to be proportional to both p and {epsilon}{sub zz}, B{sub 2} {sub perpendicular} {sub to} {proportional_to} p .{epsilon}{sub zz}. To study the influence of substrate orientation on the magnetic properties of GaMnAs, a series of GaMnAs layers with Mn contents up to 5% was grown on (001)- and (113)A-oriented GaAs substrates. The hole densities and Curie temperatures, determined from magnetotransport measurements, are drastically reduced in the (113)A layers. The differences in the magnetic properties of (113)A- and

  20. Flow stress anisotropy

    DEFF Research Database (Denmark)

    Winther, G.

    1996-01-01

    stress Variation in the rolling plane, which may be as high as 20%, are presented. The traditional Taylor model is applied to the data to account for the effect of texture. However, texture effects alone are not enough to explain all of the observed anisotropy. New models which take the combined effects...... of texture and deformation microstructure into account are presented. The models are based on the Taylor and Sachs models but modified with an anisotropic critical shear stress to account for the effect of the microstructure. The agreement between experimental data and model predictions is definitely better...

  1. Effect of interionic anisotropy on the phase states and spectra of a non-Heisenberg magnet with S = 1

    Energy Technology Data Exchange (ETDEWEB)

    Kosmachev, O. A.; Krivtsova, A. V.; Fridman, Yu. A., E-mail: yuriifridman@gmail.com [Vernadskii Crimea Federal University (Russian Federation)

    2016-02-15

    We study the effect of interionic anisotropy on the phase states of a non-Heisenberg ferromagnet with magnetic ion spin S = 1. It is shown that depending on the relation between the interionic anisotropy constants, uniaxial and angular ferromagnetic and nonmagnetic phases exist in the system. We analyze the dynamic properties of the system in the vicinity of orientational phase transitions, as well as a phase transition in the magnetic moment magnitude. It is shown that orientational phase transitions in ferromagnetic and nematic phases can be first- as well as second-order.

  2. On the Acceleration and Anisotropy of Ions Within Magnetotail Dipolarizing Flux Bundles

    Science.gov (United States)

    Zhou, Xu-Zhi; Runov, Andrei; Angelopoulos, Vassilis; Artemyev, Anton V.; Birn, Joachim

    2018-01-01

    Dipolarizing flux bundles (DFBs), earthward propagating structures with enhanced northward magnetic field Bz, are usually believed to carry a distinctly different plasma population from that in the ambient magnetotail plasma sheet. The ion distribution functions within the DFB, however, have been recently found to be largely controlled by the ion adiabaticity parameter κ in the ambient plasma sheet outside the DFB. According to these observations, the ambient κ values of 2-3 usually correspond to a strong perpendicular anisotropy of suprathermal ions within the DFB, whereas for lower κ values the DFB ions become more isotropic. Here we utilize a simple, test particle model to explore the nature of the anisotropy and its dependence on the ambient κ values. We find that the anisotropy originates from successive ion reflections and reentries to the DFB, during which the ions are consecutively accelerated in the perpendicular direction by the DFB-associated electric field. This consecutive acceleration may be interrupted, however, when magnetic field lines are highly curved in the ambient plasma sheet. In this case, the ion trajectories become stochastic outside the DFB, which makes the reflected ions less likely to return to the DFB for another cycle of acceleration; as a consequence, the perpendicular ion anisotropy does not appear. Given that the DFB ions are a free energy source for instabilities when they are injected toward Earth, our simple model (that reproduces most observational features on the anisotropic DFB ion distributions) may shed new lights on the coupling process between magnetotail and inner magnetosphere.

  3. Interfacial exchange coupling and magnetization reversal in perpendicular [Co/Ni]N/TbCo composite structures.

    Science.gov (United States)

    Tang, M H; Zhang, Zongzhi; Tian, S Y; Wang, J; Ma, B; Jin, Q Y

    2015-06-15

    Interfacial exchange coupling and magnetization reversal characteristics in the perpendicular heterostructures consisting of an amorphous ferrimagnetic (FI) TbxCo(100-x) alloy layer exchange-coupled with a ferromagnetic (FM) [Co/Ni]N multilayer have been investigated. As compared with pure TbxCo(100-x) alloy, the magnetization compensation composition of the heterostructures shift to a higher Tb content, implying Co/Ni also serves to compensate the Tb moment in TbCo layer. The net magnetization switching field Hc⊥ and interlayer interfacial coupling field Hex, are not only sensitive to the magnetization and thickness of the switched TbxCo(100-x) or [Co/Ni]N layer, but also to the perpendicular magnetic anisotropy strength of the pinning layer. By tuning the layer structure we achieve simultaneously both large Hc⊥ = 1.31 T and Hex = 2.19 T. These results, in addition to the fundamental interest, are important to understanding of the interfacial coupling interaction in the FM/FI heterostructures, which could offer the guiding of potential applications in heat-assisted magnetic recording or all-optical switching recording technique.

  4. Perpendicular magnetic tunnel junction with a strained Mn-based nanolayer

    Science.gov (United States)

    Suzuki, K. Z.; Ranjbar, R.; Okabayashi, J.; Miura, Y.; Sugihara, A.; Tsuchiura, H.; Mizukami, S.

    2016-07-01

    A magnetic tunnel junction with a perpendicular magnetic easy-axis (p-MTJ) is a key device for spintronic non-volatile magnetoresistive random access memory (MRAM). Co-Fe-B alloy-based p-MTJs are being developed, although they have a large magnetisation and medium perpendicular magnetic anisotropy (PMA), which make it difficult to apply them to a future dense MRAM. Here, we demonstrate a p-MTJ with an epitaxially strained MnGa nanolayer grown on a unique CoGa buffer material, which exhibits a large PMA of more than 5 Merg/cm3 and magnetisation below 500 emu/cm3 these properties are sufficient for application to advanced MRAM. Although the experimental tunnel magnetoresistance (TMR) ratio is still low, first principles calculations confirm that the strain-induced crystal lattice distortion modifies the band dispersion along the tetragonal c-axis into the fully spin-polarised state; thus, a huge TMR effect can be generated in this p-MTJ.

  5. Thickness dependence of magnetic anisotropy and intrinsic anomalous Hall effect in epitaxial Co{sub 2}MnAl film

    Energy Technology Data Exchange (ETDEWEB)

    Meng, K.K., E-mail: kkmeng@ustb.edu.cn [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Miao, J.; Xu, X.G. [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Zhao, J.H. [State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083 (China); Jiang, Y. [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China)

    2017-04-04

    We have investigated the thickness dependence of magnetic anisotropy and intrinsic anomalous Hall effect (AHE) in single-crystalline full-Heusler alloy Co{sub 2}MnAl (CMA) grown by molecular-beam epitaxy on GaAs(001). The magnetic anisotropy is the interplay of uniaxial and the fourfold anisotropy, and the corresponding anisotropy constants have been deduced. Considering the thickness of CMA is small, we ascribe it to the influence from interface stress. The AHE in CMA is found to be well described by a proper scaling. The intrinsic anomalous conductivity is found to be smaller than the calculated one and is thickness dependent, which is ascribed to the influence of chemical ordering by affecting the band structure and Fermi surface. - Highlights: • Single-crystalline full-Heusler alloy Co{sub 2}MnAl grown by molecular-beam epitaxy. • Uniaxial and the fourfold magnetic anisotropies in Heusler alloys. • Anomalous Hall effect in Heusler alloys. • The intrinsic contributions modified by chemical ordering.

  6. Induced anisotropy in amorphous Sm-Co sputtered films

    International Nuclear Information System (INIS)

    Chen, K.; Hegde, H.; Cadieu, F.J.

    1992-01-01

    The variation of the in-the-film-plane anisotropy constant, K u , with composition and the magnitude of the field, H s , applied in plane during the sputter deposition of amorphous Sm x Co 1-x , 0.08≤x≤0.40, thin films has been studied. We demonstrate here that with a large H s , 5.0 kOe, a well defined and large in-the-film-plane anisotropy can be obtained. An exceptionally high value of K u =3.3x10 6 erg/cm 3 has been obtained. For the loop measured along the in-plane hard direction, the opening of the loop was undetectable, and the loop along the easy axis was a perfect rectangle. For certain conditions, the anisotropy field measured perpendicular to the film plane when corrected for demagnetization (N d =4π) was the same as that for the in-plane measurements. It is concluded that surface induced short range ordering was the origin of the anisotropy observed in amorphous films deposited in a magnetic field. The formation mechanism is different from that of the short range ordering induced by field annealing

  7. Magnetic Anisotropy by Rashba Spin-Orbit Coupling in Antiferromagnetic Thin Films

    Science.gov (United States)

    Ieda, Jun'ichi; Barnes, Stewart E.; Maekawa, Sadamichi

    2018-05-01

    Magnetic anisotropy in an antiferromagnet (AFM) with inversion symmetry breaking (ISB) is investigated. The magnetic anisotropy energy (MAE) resulting from the Rashba spin-orbit and s-d type exchange interactions is determined for two different models of AFMs. The global ISB model, representing the effect of a surface, an interface, or a gating electric field, results in an easy-plane magnetic anisotropy. In contrast, for a local ISB model, i.e., for a noncentrosymmetric AFM, perpendicular magnetic anisotropy (PMA) arises. Both results differ from the ferromagnetic case, in which the result for PMA depends on the band structure and dimensionality. These MAE contributions play a key role in determining the direction of the Néel order parameter in antiferromagnetic nanostructures, and reflect the possibility of electrical-field control of the Néel vector.

  8. Geometry anisotropy and mechanical property isotropy in titanium foam fabricated by replica impregnation method

    Energy Technology Data Exchange (ETDEWEB)

    Manonukul, Anchalee, E-mail: anchalm@mtec.or.th [National Metal and Materials Technology Center (MTEC), National Science and Technology Development Agency (NSTDA), 114 Thailand Science Park, Paholyothin Rd., Klong 1, Klong Luang, Pathumthani 12120 (Thailand); Srikudvien, Pathompoom [National Metal and Materials Technology Center (MTEC), National Science and Technology Development Agency (NSTDA), 114 Thailand Science Park, Paholyothin Rd., Klong 1, Klong Luang, Pathumthani 12120 (Thailand); Tange, Makiko [Taisei Kogyo Thailand Co., Ltd., Room INC2d-409, Innovation Cluster 2 Building, Tower D, 141 Thailand Science Park, Paholyothin Rd., Klong 1, Klong Luang, Pathumthani 12120 (Thailand); Puncreobutr, Chedtha [Department of Metallurgical Engineering, Faculty of Engineering, Chulalongkorn University, Pathumwan, Bangkok 10330 (Thailand)

    2016-02-08

    Polyurethane (PU) foams have both geometry and mechanical property anisotropy. Metal foams, which are manufacturing by investment casting or melt deposition method and using PU foam as a template, also have mechanical property anisotropy. This work studied the mechanical properties in two directions of titanium foam with four different cell sizes fabricated using the replica impregnation method. The two directions are (1) the loading direction parallel to the foaming direction where the cells are elongated (EL direction) and (2) the loading direction perpendicular to the foaming direction where the cell are equiaxed (EQ direction). The results show that the compression responses for both EL and EQ directions are isotropy. Micrographs and X-ray micro-computed tomography show that the degree of geometry anisotropy is not strong enough to results in mechanical property anisotropy.

  9. Geometry anisotropy and mechanical property isotropy in titanium foam fabricated by replica impregnation method

    International Nuclear Information System (INIS)

    Manonukul, Anchalee; Srikudvien, Pathompoom; Tange, Makiko; Puncreobutr, Chedtha

    2016-01-01

    Polyurethane (PU) foams have both geometry and mechanical property anisotropy. Metal foams, which are manufacturing by investment casting or melt deposition method and using PU foam as a template, also have mechanical property anisotropy. This work studied the mechanical properties in two directions of titanium foam with four different cell sizes fabricated using the replica impregnation method. The two directions are (1) the loading direction parallel to the foaming direction where the cells are elongated (EL direction) and (2) the loading direction perpendicular to the foaming direction where the cell are equiaxed (EQ direction). The results show that the compression responses for both EL and EQ directions are isotropy. Micrographs and X-ray micro-computed tomography show that the degree of geometry anisotropy is not strong enough to results in mechanical property anisotropy.

  10. Small angle scattering methods to study porous materials under high uniaxial strain

    Energy Technology Data Exchange (ETDEWEB)

    Le Floch, Sylvie, E-mail: sylvie.le-floch@univ-lyon1.fr; Balima, Félix; Pischedda, Vittoria; Legrand, Franck; San-Miguel, Alfonso [Institut Lumière Matière, UMR5306 Université Lyon 1-CNRS, Université de Lyon, 69622 Villeurbanne Cedex (France)

    2015-02-15

    We developed a high pressure cell for the in situ study of the porosity of solids under high uniaxial strain using neutron small angle scattering. The cell comprises a hydraulically actioned piston and a main body equipped with two single-crystal sapphire windows allowing for the neutron scattering of the sample. The sample cavity is designed to allow for a large volume variation as expected when compressing highly porous materials. We also implemented a loading protocol to adapt an existing diamond anvil cell for the study of porous materials by X-ray small angle scattering under high pressure. The two techniques are complementary as the radiation beam and the applied pressure are in one case perpendicular to each other (neutron cell) and in the other case parallel (X-ray cell). We will illustrate the use of these two techniques in the study of lamellar porous systems up to a maximum pressure of 0.1 GPa and 0.3 GPa for the neutron and X-ray cells, respectively. These devices allow obtaining information on the evolution of porosity with pressure in the pore dimension subdomain defined by the wave-numbers explored in the scattering process. The evolution with the applied load of such parameters as the fractal dimension of the pore-matrix interface or the apparent specific surface in expanded graphite and in expanded vermiculite is used to illustrate the use of the high pressure cells.

  11. Uniaxial compression on the superconductivity of {beta}-BDA-TTP salts

    Energy Technology Data Exchange (ETDEWEB)

    Ito, Hiroshi; Ishihara, Tetsuo; Tanaka, Hisaaki; Kuroda, Shin-ichi [Department of Applied Physics, Nagoya University, Chikusa, Nagoya, 464-8603 (Japan); Yamada, Jun-ichi [Department of Material Science, University of Hyogo, 3-2-1 Kouto, Kamigori-cho, Hyogo 678-1297 (Japan)], E-mail: ito@nuap.nagoya-u.ac.jp

    2008-10-15

    The {beta}-type BDA-TTP superconductors attract attention due to the high transition temperature Tc at ambient pressure for organic superconductors. In order to get insight into the superconductivity in terms of the dimerized anisotropic triangular lattice model, Tc of {beta}-(BDA-TTP){sub 2}X [X = SbF{sub 6}, X = AsF{sub 6}] is studied under uniaxial compression by resistivity measurements. Under compression parallel to the donor stack, Tc increases gradually up to 3 (X = SbF{sub 6}), 5 (X = AsF{sub 6}) kbar, and decreases under further piston pressure. Under compression perpendicular to the donor stack, Tc decreases gradually up to 2.5 (X = SbF{sub 6}), 4 (X = AsF{sub 6}) kbar and then decreases rapidly under further pressure. Only for X = AsF{sub 6}, a Tc minimum at 3 kbar is found for both direction. These trends in Tc are understood as an interplay between the enhancement of antiferromagnetic spin fluctuation and frustration on the triangular lattice. By the interplane compression, Tc increased by 0.5 K up to 2 kbar for both salts, demonstrating the importance of the interlayer interaction.

  12. Uniaxial compression on the superconductivity of β-BDA-TTP salts

    International Nuclear Information System (INIS)

    Ito, Hiroshi; Ishihara, Tetsuo; Tanaka, Hisaaki; Kuroda, Shin-ichi; Yamada, Jun-ichi

    2008-01-01

    The β-type BDA-TTP superconductors attract attention due to the high transition temperature Tc at ambient pressure for organic superconductors. In order to get insight into the superconductivity in terms of the dimerized anisotropic triangular lattice model, Tc of β-(BDA-TTP) 2 X [X = SbF 6 , X = AsF 6 ] is studied under uniaxial compression by resistivity measurements. Under compression parallel to the donor stack, Tc increases gradually up to 3 (X = SbF 6 ), 5 (X = AsF 6 ) kbar, and decreases under further piston pressure. Under compression perpendicular to the donor stack, Tc decreases gradually up to 2.5 (X = SbF 6 ), 4 (X = AsF 6 ) kbar and then decreases rapidly under further pressure. Only for X = AsF 6 , a Tc minimum at 3 kbar is found for both direction. These trends in Tc are understood as an interplay between the enhancement of antiferromagnetic spin fluctuation and frustration on the triangular lattice. By the interplane compression, Tc increased by 0.5 K up to 2 kbar for both salts, demonstrating the importance of the interlayer interaction.

  13. Uniaxial compression on the superconductivity of β-BDA-TTP salts

    Science.gov (United States)

    Ito, Hiroshi; Ishihara, Tetsuo; Tanaka, Hisaaki; Kuroda, Shin-ichi; Yamada, Jun-ichi

    2008-10-01

    The β-type BDA-TTP superconductors attract attention due to the high transition temperature Tc at ambient pressure for organic superconductors. In order to get insight into the superconductivity in terms of the dimerized anisotropic triangular lattice model, Tc of β-(BDA-TTP)2X [X = SbF6, X = AsF6] is studied under uniaxial compression by resistivity measurements. Under compression parallel to the donor stack, Tc increases gradually up to 3 (X = SbF6), 5 (X = AsF6) kbar, and decreases under further piston pressure. Under compression perpendicular to the donor stack, Tc decreases gradually up to 2.5 (X = SbF6), 4 (X = AsF6) kbar and then decreases rapidly under further pressure. Only for X = AsF6, a Tc minimum at 3 kbar is found for both direction. These trends in Tc are understood as an interplay between the enhancement of antiferromagnetic spin fluctuation and frustration on the triangular lattice. By the interplane compression, Tc increased by 0.5 K up to 2 kbar for both salts, demonstrating the importance of the interlayer interaction.

  14. Enhanced electron-lattice coupling under uniaxial stress in layered double hydroxides intercalated with samarium complexes

    International Nuclear Information System (INIS)

    Park, Ta-Ryeong

    2004-01-01

    We have applied uniaxial stress to samarium complexes by intercalating them into the gallery of a layered material and by using a diamond-anvil cell at 28 K. Although uniaxial stress reduces symmetry and removes degeneracy, the overall number of photoluminescence (PL) peaks evidently decreased with the application of uniaxial stress. This contradictory observation is explained by an increased electron-lattice coupling strength under uniaxial stress. This behavior is also confirmed by time-resolved PL data.

  15. Estimation of air void and aggregate spatial distributions in concrete under uniaxial compression using computer tomography scanning

    International Nuclear Information System (INIS)

    Wong, R.C.K.; Chau, K.T.

    2005-01-01

    Normal- and high-strength concrete cylinders (designed compressive strengths of 30 and 90 MPa at 28 days) were loaded uniaxially. Computer tomography (CT) scanning technique was used to examine the evolution of air voids inside the specimens at various loading states up to 85% of the ultimate compressive strength. The normal-strength concrete yielded a very different behaviour in changes of internal microstructure as compared to the high-strength concrete. There were significant instances of nucleation and growth in air voids in the normal-strength concrete specimen, while the increase in air voids in the high-strength concrete specimen was insignificant. In addition, CT images were used for mapping the aggregate spatial distributions within the specimens. No intrinsic anisotropy was detected from the fabric analysis

  16. Light propagation in two-dimensional photonic crystals based on uniaxial polar materials: results on polaritonic spectrum

    Science.gov (United States)

    Gómez-Urrea, H. A.; Duque, C. A.; Pérez-Quintana, I. V.; Mora-Ramos, M. E.

    2017-03-01

    The dispersion relations of two-dimensional photonic crystals made of uniaxial polaritonic cylinders arranged in triangular lattice are calculated. The particular case of the transverse magnetic polarization is taken into account. Three different uniaxial materials showing transverse phonon-polariton excitations are considered: aluminum nitride, gallium nitride, and indium nitride. The study is carried out by means of the finite-difference time-domain technique for the solution of Maxwell equations, together with the method of the auxiliary differential equation. It is shown that changing the filling fraction can result in the modification of both the photonic and polaritonic bandgaps in the optical dispersion relations. Wider gaps appear for smaller filling fraction values, whereas a larger number of photonic bandgaps will occur within the frequency range considered when a larger filling fraction is used. The effect of including the distinct wurtzite III-V nitride semiconductors as core materials in the cylinders embedded in the air on the photonic properties is discussed as well, highlighting the effect of the dielectric anisotropy on the properties of the polaritonic part of the photonic spectrum.

  17. Seismic Anisotropy of Soft Sands, Offshore Western AUstralia

    Science.gov (United States)

    Urosevic, M.; Gurevich, B.

    2007-05-01

    the VSP data. Further analysis of the soft sand anisotropy was conducted on surface seismic data. Magnitude of the overlain shale anisotropy was first established by measurements in the dominant horizontal stress direction. Subsequently pre-stack reflection amplitudes measured along several azimuths were matched to expected amplitudes from anisotropic AVO modelling. The results indicate that the anisotropy of the reservoir sands is high (more than 10%) at sonic frequencies but weak (about 2-3%), at seismic frequencies. We think this anisotropy is caused by the preferential closure of compliant inter-granular contacts oriented perpendicular to the principal horizontal stress. The effect is weaker at seismic frequencies since the wavelength in this case involves shales as well as sand. Furthermore, sonic anisotropy could have also been affected by the local stress conditions around the wellbore.

  18. Effect of uniaxial strain on the quantum critical phase of Sr{sub 3}Ru{sub 2}O{sub 7}

    Energy Technology Data Exchange (ETDEWEB)

    Barber, Mark E.; Brodsky, Daniel O.; Mackenzie, Andrew P. [Scottish Universities Physics Alliance (SUPA), School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS (United Kingdom); Max Planck Institute for Chemical Physics of Solids, Noethnitzer Strasse 40, Dresden 01187 (Germany); Hicks, Clifford W. [Max Planck Institute for Chemical Physics of Solids, Noethnitzer Strasse 40, Dresden 01187 (Germany); Perry, Robin [School of Physics and Astronomy, University of Edinburgh, Edinburgh EH9 3FD (United Kingdom)

    2016-07-01

    Sr{sub 3}Ru{sub 2}O{sub 7} has a metamagnetic quantum critical endpoint, which in highly pure samples is masked by a novel phase. This phase is isotropic in the absence of symmetry-breaking fields, but weak in-plane magnetic fields are well-known to induce strong resistive anisotropy, leading to speculation that the phase intrinsically breaks the tetragonal symmetry of the lattice. We have used uniaxial strain to break the symmetry of the lattice and have found a dramatic response: compression by 0.1%, for example, induces a resistive anisotropy of ∝ 2.5. I will discuss these results in the context of the underlying symmetry of the anomalous phase.

  19. Discoveries that guided the beginning of perpendicular magnetic recording

    International Nuclear Information System (INIS)

    Iwasaki, S.

    2001-01-01

    The speculations and discoveries that guided the beginning of perpendicular magnetic recording, which have never been systematically discussed before, are described in this paper. Especially, four important discoveries of perpendicular magnetization, Co-Cr film, effect of double layered medium, and complementarity law are described in detail. The studies on thin film media and recording mechanisms at short wavelengths aiming at the advancement of longitudinal magnetic recording in the 1960's lead to the realization of the new perpendicular magnetic recording through these discoveries. None of these works was on any list of research targets in the 1960's. The study of perpendicular magnetic recording has taught us that research should proceed systematically with definite targets and that it is important to have an attitude not to neglect phenomena that are different from the common sense at the time

  20. Prediction of hole expansion ratio for various steel sheets based on uniaxial tensile properties

    Science.gov (United States)

    Kim, Jae Hyung; Kwon, Young Jin; Lee, Taekyung; Lee, Kee-Ahn; Kim, Hyoung Seop; Lee, Chong Soo

    2018-01-01

    Stretch-flangeability is one of important formability parameters of thin steel sheets used in the automotive industry. There have been many attempts to predict hole expansion ratio (HER), a typical term to evaluate stretch-flangeability, using uniaxial tensile properties for convenience. This paper suggests a new approach that uses total elongation and average normal anisotropy to predict HER of thin steel sheets. The method provides a good linear relationship between HER of the machined hole and the predictive variables in a variety of materials with different microstructures obtained using different processing methods. The HER of the punched hole was also well predicted using the similar approach, which reflected only the portion of post uniform elongation. The physical meaning drawn by our approach successfully explained the poor HER of austenitic steels despite their considerable elongation. The proposed method to predict HER is simple and cost-effective, so it will be useful in industry. In addition, the model provides a physical explanation of HER, so it will be useful in academia.

  1. Structure of vortices in superfluid 3He A-like phase in uniaxially stretched aerogel

    International Nuclear Information System (INIS)

    Aoyama, Kazushi; Ikeda, Ryusuke

    2009-01-01

    Possible vortex-core transitions in A-like phase of superfluid 3 He in uniaxially stretched aerogel are investigated. Since the global anisotropy in this system induces the polar pairing state in a narrow range close to the superfluid transition in addition to the A-like and B-like phases, the polar state may occur in the core of a vortex in the A-like phase identified with the ABM pairing state, like in the case of the bulk B phase where a core including the ABM state is realized at higher pressures. We examine the core structure of a single vortex under the boundary condition compatible with the Mermin-Ho vortex in the presence of the dipole interaction. Following Salomaa and Volovik's approach, we numerically solve the Ginzburg-Landau equation for an axially symmetric vortex and, by examining its stability against nonaxisymmetric perturbations, discuss possible vortex core states. It is found that a first order transition on core states may occur on warming from an axisymmetric vortex with a nonunitary core to a singular vortex with the polar core.

  2. Structure of vortices in superfluid 3He A-like phase in uniaxially stretched aerogel

    Science.gov (United States)

    Aoyama, Kazushi; Ikeda, Ryusuke

    2009-02-01

    Possible vortex-core transitions in A-like phase of superfluid 3He in uniaxially stretched aerogel are investigated. Since the global anisotropy in this system induces the polar pairing state in a narrow range close to the superfluid transition in addition to the A-like and B-like phases, the polar state may occur in the core of a vortex in the A-like phase identified with the ABM pairing state, like in the case of the bulk B phase where a core including the ABM state is realized at higher pressures. We examine the core structure of a single vortex under the boundary condition compatible with the Mermin-Ho vortex in the presence of the dipole interaction. Following Salomaa and Volovik's approach, we numerically solve the Ginzburg-Landau equation for an axially symmetric vortex and, by examining its stability against nonaxisymmetric perturbations, discuss possible vortex core states. It is found that a first order transition on core states may occur on warming from an axisymmetric vortex with a nonunitary core to a singular vortex with the polar core.

  3. Magnetization reversal of in-plane uniaxial Co films and its dependence on epitaxial alignment

    Energy Technology Data Exchange (ETDEWEB)

    Idigoras, O., E-mail: o.idigoras@nanogune.eu; Suszka, A. K.; Berger, A. [CIC nanoGUNE Consolider, Tolosa Hiribidea 76, E-20018 Donostia-San Sebastian (Spain); Vavassori, P. [CIC nanoGUNE Consolider, Tolosa Hiribidea 76, E-20018 Donostia-San Sebastian (Spain); IKERBASQUE, The Basque Foundation for Science, E-48011 Bilbao (Spain); Obry, B.; Hillebrands, B. [Fachbereich Physik and Landesforschungzentrum OPTIMAS, Technische Universität Kaiserslautern, Erwin-Schrödinger-Straße 56, D-67663 Kaiserslautern (Germany); Landeros, P. [Departamento de Física, Universidad Técnica Federico Santa María, Avenida España 1680, 2390123 Valparaíso (Chile)

    2014-02-28

    This work studies the influence of crystallographic alignment onto magnetization reversal in partially epitaxial Co films. A reproducible growth sequence was devised that allows for the continuous tuning of grain orientation disorder in Co films with uniaxial in-plane anisotropy by the controlled partial suppression of epitaxy. While all stable or meta-stable magnetization states occurring during a magnetic field cycle exhibit a uniform magnetization for fully epitaxial samples, non-uniform states appear for samples with sufficiently high grain orientation disorder. Simultaneously with the occurrence of stable domain states during the magnetization reversal, we observe a qualitative change of the applied field angle dependence of the coercive field. Upon increasing the grain orientation disorder, we observe a disappearance of transient domain wall propagation as the dominating reversal process, which is characterized by an increase of the coercive field for applied field angles away from the easy axis for well-ordered epitaxial samples. Upon reaching a certain disorder threshold level, we also find an anomalous magnetization reversal, which is characterized by a non-monotonic behavior of the remanent magnetization and coercive field as a function of the applied field angle in the vicinity of the nominal hard axis. This anomaly is a collective reversal mode that is caused by disorder-induced frustration and it can be qualitatively and even quantitatively explained by means of a two Stoner-Wohlfarth particle model. Its predictions are furthermore corroborated by Kerr microscopy and by Brillouin light scattering measurements.

  4. Electrical resistivity of CeNiSn under uniaxial and hydrostatic pressures

    Science.gov (United States)

    Echizen, Y.; Umeo, K.; Igaue, T.; Takabatake, T.

    2002-05-01

    We present measurements of the electrical resistivity ρ(T) on high-quality single-crystalline CeNiSn under both hydrostatic pressure up to 1 GPa and uniaxial pressure up to 0.25 GPa. At ambient pressure, ρ(T) along the orthorhombic a-axis (b-axis) shows two maxima at TL = 12 K (14 K) and TH = 74 K (40 K), respectively, which arise from the Kondo scattering of conduction electrons by the crystal-field ground state and excited states. With increasing hydrostatic pressure, both TL and TH increase linearly, and for P≥0.8 GPa, the anisotropy in ρ(T) for I∥a and I∥b almost vanishes as a result of increased hybridization between the 4f electrons and the conduction electrons. Under P∥a, both TL and TH in ρ(I∥b) increase similarly to under hydrostatic pressure. Under P∥c, however, the depression of TL in ρ(I∥a) and ρ(I∥b) suggests that the c-f hybridization in the crystal-field ground state is weakened in the a-b plane of CeNiSn.

  5. Periodic reversal of magneto-optic Faraday rotation on uniaxial birefringence crystal with ultrathin magnetic films

    Directory of Open Access Journals (Sweden)

    C. W. Su

    2013-07-01

    Full Text Available An experimental approach of inclined incidence magneto-optic Faraday effect observed in the polar plane is applied. Three samples containing ferromagnetic cobalt ultrathin films on a semiconductor zinc oxide (0001 single crystal substrate with in-plane and out-of-plane anisotropy are evaluated. Through the fine adjustment of crossed polarizers in the magneto-optic effect measurement completely recorded the detail optical and magneto-optical responses from the birefringent crystal substrate and the magnetic film, especially for the signal induced from the substrate with uniaxial optical axis. The angle dependency of interference phenomena periodically from the optical and magneto-optical responses is attributed to the birefringence even in the absence of a magnetic field. The new type of observation finds that the transmission Faraday intensity in the oblique incidence includes a combination of polarization rotations, which results from optical compensation from the substrate and magneto-optical Faraday effects from the film. The samples grown at different rates and examined by this method exhibit magnetic structure discriminations. This result can be applied in the advanced polarized-light technologies to enhance the spatial resolution of magnetic surfaces with microstructural information under various magnetic field direction.

  6. Modeling of Perpendicularly Driven Dual-Frequency Capacitively Coupled Plasma

    International Nuclear Information System (INIS)

    Wang Hongyu; Sun Peng; Zhao Shuangyun; Li Yang; Jiang Wei

    2016-01-01

    We analyzed perpendicularly configured dual-frequency (DF) capacitively coupled plasmas (CCP). In this configuration, two pairs of electrodes are arranged oppositely, and the discharging is perpendicularly driven by two radio frequency (RF) sources. Particle-in-cell/Monte Carlo (PIC/MC) simulation showed that the configuration had some advantages as this configuration eliminated some dual frequency coupling effects. Some variation and potential application of the discharging configuration is discussed briefly. (paper)

  7. Effect of pressure anisotropy on the m=1 small wavelength modes in Z-pinches

    Energy Technology Data Exchange (ETDEWEB)

    Faghihi, M. (Royal Inst. of Tech., Stockholm, Sweden. Dept. of Plasma Physics and Fusion Research)

    1987-05-01

    A generalization of Freidberg's perpendicular MHD model is used to investigate the effect of pressure anisotropy on the small wavelength internal kink (m=1) mode instability in a Z-Pinch. A normal mode analysis of perturbed motion of an incompressible, collisionless and cylindrical plasma is performed. The stability criterion is (r{SIGMA}B{sup 2})' {le} 0, where {SIGMA} = 1 - (P{sub parallel} - P{sub perpendicular} {sub to})/B/sup 2/. It cannot be fulfilled without violation of the fire hose stability condition {SIGMA} {ge} 0.

  8. Effect of pressure anisotropy on the m=1 small wavelength modes in Z-pinches

    International Nuclear Information System (INIS)

    Faghihi, M.

    1987-01-01

    A generalization of Freidberg's perpendicular MHD model is used to investigate the effect of pressure anisotropy on the small wavelength internal kink (m=1) mode instability in a Z-Pinch. A normal mode analysis of perturbed motion of an incompressible, collisionless and cylindrical plasma is performed. The stability criterion is (rΣB 2 )' ≤ 0, where Σ = 1 - (P parallel - P perpendicular to )/B 2 . It cannot be fulfilled without violation of the fire hose stability condition Σ ≥ 0. (orig.)

  9. Anisotropy in electron-atom collisions

    International Nuclear Information System (INIS)

    Linden van den Heuvel, H.B. van.

    1982-01-01

    Most of the work described in this thesis deals with studies using coincidence experiments, particularly for investigating the electron impact excitation of the 2 1 P and 3 1 D states in helium. A peculiarity is that in the 3 1 D studies the directly emitted 3 1 D → 2 1 P photons are not observed but the 2 1 P → 1 1 S photons resulting from the 3 1 D → 2 1 P → 1 1 S cascade instead. Another interesting point is the choice of the quantisation axis. The author demonstrates that it is of great advantage to take the quantisation axis perpendicular to the scattering plane rather than in the direction of the incident beam, as was done (on historical grounds) in previously reported electron-photon coincidence experiments. Contrary to the incident beam direction the axis perpendicular to the scattering plane really represents an axis of symmetry in the coincidence experiment. In Chapter II the so-called 'parity unfavoured' excitation of the (2p 2 ) 3 P state of helium by electrons is studied. In chapter III the anisotropy parameters for the electron impact excitation of the 2 1 P state of helium in the energy range from 26.6 to 40 eV and in the angular range from 30 0 to 110 0 are determined. Chapter IV contains a description of a scattered electron cascaded-photon coincidence experiment on the electron impact excitation of helium's 3 1 D state. The measurement of complex scattering amplitudes for electron impact excitation of the 3 1 D and 3 1 P states of helium is discussed in Chapter V. (Auth./C.F.)

  10. Effect of combined external uniaxial stress and dc bias on the dielectric property of BaTiO3-based dielectrics in multilayer ceramic capacitor: thermodynamics and experiments

    International Nuclear Information System (INIS)

    Yang Gang; Yue Zhenxing; Sun Tieyu; Gou Huanlin; Li Longtu

    2008-01-01

    The dielectric properties of (Nb, Y)-doped BaTiO 3 in a multilayer ceramic capacitor (MLCC) under combined external uniaxial compressive stress and dc bias field were investigated at room temperature by using a modified Ginsburg-Landau-Devonshire thermodynamic theory and the dielectric measurement. It is found that although dc bias decreases the dielectric properties dominantly, the influence of the external uniaixial compressive stress should not be neglected. When applied along a direction perpendicular to the internal electrode layer in the MLCC, the external uniaixal compressive stress will strengthen the negative effect of dc bias. In contrast, the external uniaxial compressive stress along a direction parallel to the internal electrode layer in the MLCC will increase the dielectric permittivity under dc bias field, i.e. improve the ε-V response of the MLCC. Furthermore, although there is a difference between the calculated permittivity and the measured permittivity, the effects of the combined external uniaxial compressive stress and dc bias field on the dielectric permittivity described through two approaches are in good agreement

  11. Transport current anisotropy in oriented grained bulk YBa2Cu3O(x) superconductor

    International Nuclear Information System (INIS)

    Selvamanickam, V.; Salama, K.

    1990-01-01

    The anisotropy in transport current density has been studied on bulk YBa2Cu3O(x) superconductor. The transport current density measurements were performed on oriented grained YBa2Cu3O(x) superconductor with the current aligned at different angles to the a-b plane. The angular dependence of Jc shows a rapid drop when the transport current is misaligned from the a-b plane at small angles and then a slow decrease at higher angles. An anisotropy ratio of about 25 is observed at 77 K and zero field between the Jc along a-b plane and that perpendicular to the plane. 15 refs

  12. Transport current anisotropy in oriented grained bulk YBa2Cu3Ox superconductor

    International Nuclear Information System (INIS)

    Selvamanickam, V.; Salama, K.

    1990-01-01

    The anisotropy in transport current density has been studied on bulk YBa 2 Cu 3 O x superconductor. The transport current density measurements were performed on oriented grained YBa 2 Cu 3 O x superconductor with the current aligned at different angles to the a endash b plane. The angular dependence of J c shows a rapid drop when the transport current is misaligned from the a endash b plane at small angles and then a slow decrease at higher angles. An anisotropy ratio of about 25 is observed at 77 K and zero field between the J c along a endash b plane and that perpendicular to the plane

  13. Manipulating magnetic anisotropy of the ultrathin Co{sub 2}FeAl full-Heusler alloy film via growth orientation of the Pt buffer layer

    Energy Technology Data Exchange (ETDEWEB)

    Wen, F.S., E-mail: wenfsh03@126.com [State Key Lab of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Xiang, J.Y.; Hao, C.X.; Zhang, F.; Lv, Y.F. [State Key Lab of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Wang, W.H. [Institute of Physics, Chinese Academy of Science, Beijing 100080 (China); Hu, W.T.; Liu, Z.Y. [State Key Lab of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China)

    2013-12-15

    The ultrathin films of Co{sub 2}FeAl (CFA) full-Heusler alloy were prepared between two Pt layers on MgO single crystals by magnetron sputtering. By controlling the substrate temperature, different growth orientations of the Pt underlayers were realized, and their effects were investigated on the magnetic anisotropy of the ultrathin CFA film. It was revealed that different Pt orientations lead to distinctly different magnetic anisotropy for the sandwiched ultrathin CFA films. The Pt (111) orientation favors the perpendicular anisotropy, while the appearance of partial Pt (001) orientation leads to the quick decrease of perpendicular anisotropy and the complete Pt (001) orientation gives rise to the in-plane anisotropy. With the Pt (111) orientation, the temperature and thickness-induced spin reorientation transitions were investigated in the sandwiched ultrathin CFA films. - Highlights: • Different Pt orientations lead to different magnetic anisotropy for sandwiched ultrathin CFA films. • The Pt (111) orientation favors the perpendicular anisotropy for CFA layer. • Temperature and thickness-induced spin reorientation transitions were investigated in sandwiched ultrathin CFA films. • 0.8 nm CFA film is good candidate as electrode in magnetic tunnel junctions.

  14. Manipulating magnetic anisotropy of the ultrathin Co2FeAl full-Heusler alloy film via growth orientation of the Pt buffer layer

    International Nuclear Information System (INIS)

    Wen, F.S.; Xiang, J.Y.; Hao, C.X.; Zhang, F.; Lv, Y.F.; Wang, W.H.; Hu, W.T.; Liu, Z.Y.

    2013-01-01

    The ultrathin films of Co 2 FeAl (CFA) full-Heusler alloy were prepared between two Pt layers on MgO single crystals by magnetron sputtering. By controlling the substrate temperature, different growth orientations of the Pt underlayers were realized, and their effects were investigated on the magnetic anisotropy of the ultrathin CFA film. It was revealed that different Pt orientations lead to distinctly different magnetic anisotropy for the sandwiched ultrathin CFA films. The Pt (111) orientation favors the perpendicular anisotropy, while the appearance of partial Pt (001) orientation leads to the quick decrease of perpendicular anisotropy and the complete Pt (001) orientation gives rise to the in-plane anisotropy. With the Pt (111) orientation, the temperature and thickness-induced spin reorientation transitions were investigated in the sandwiched ultrathin CFA films. - Highlights: • Different Pt orientations lead to different magnetic anisotropy for sandwiched ultrathin CFA films. • The Pt (111) orientation favors the perpendicular anisotropy for CFA layer. • Temperature and thickness-induced spin reorientation transitions were investigated in sandwiched ultrathin CFA films. • 0.8 nm CFA film is good candidate as electrode in magnetic tunnel junctions

  15. Uniaxially stressed Ge:Ga and Ge:Be

    Energy Technology Data Exchange (ETDEWEB)

    Dubon, Jr., Oscar Danilo [Univ. of California, Berkeley, CA (United States)

    1992-12-01

    The application of a large uniaxial stress to p-type Ge single crystals changes the character of both the valence band and the energy levels associated with the acceptors. Changes include the splitting of the fourfold degeneracy of the valence band top and the reduction of the ionization energy of shallow acceptors. In order to study the effect of uniaxial stress on transport properties of photoexcited holes, a variable temperature photo-Hall effect system was built in which stressed Ge:Ga and Ge:Be could be characterized. Results indicate that stress increases the lifetime and Hall mobility of photoexcited holes. These observations may help further the understanding of fundamental physical processes that affect the performance of stressed Ge photoconductors including the capture of holes by shallow acceptors.

  16. Crystallinity of polyethylene in uni-axial extensional flow

    DEFF Research Database (Denmark)

    Wingstrand, Sara Lindeblad; van Drongelen, Martin; Mortensen, Kell

    Flow history of polymer melts in processing greatly influences the crystallinity and hence the solid properties of the final material. A wide range of polymer processes involve extensional flows e.g. fiber spinning, blow moulding etc. However, due to instrumental difficulties, experimental studies...... on polymer crystallization in controlled uniaxial extension are quite rare compared to studies of crystallization in shear. Inherently uniaxial extensional flows are strong and simple relative to shear flows, in the sense that chain stretch is easily obtained and that the molecules experience no tumbling...... such that crystallization from a stretched state can take place. In this work we explore this feature in the attempt to link the nonlinear extensional rheology to the final morphology. We investigate polyethylenes (PE) of various chain architectures and observe that, even for complex architectures like long chain branched...

  17. Seismic anisotropies of the Songshugou peridotites (Qinling orogen, central China) and their seismic implications

    Science.gov (United States)

    Cao, Yi; Jung, Haemyeong; Song, Shuguang

    2018-01-01

    Though extensively studied, the roles of olivine crystal preferred orientations (CPOs or fabrics) in affecting the seismic anisotropies in the Earth's upper mantle are rather complicated and still not fully known. In this study, we attempted to address this issue by analyzing the seismic anisotropies [e.g., P-wave anisotropy (AVp), S-wave polarization anisotropy (AVs), radial anisotropy (ξ), and Rayleigh wave anisotropy (G)] of the Songshugou peridotites (dunite dominated) in the Qinling orogen in central China, based on our previously reported olivine CPOs. The seismic anisotropy patterns of olivine aggregates in our studied samples are well consistent with the prediction for their olivine CPO types; and the magnitude of seismic anisotropies shows a striking positive correlation with equilibrium pressure and temperature (P-T) conditions. Significant reductions of seismic anisotropies (AVp, max. AVs, and G) are observed in porphyroclastic dunite compared to coarse- and fine-grained dunites, as the results of olivine CPO transition (from A-/D-type in coarse-grained dunite, through AG-type-like in porphyroclastic dunite, to B-type-like in fine-grained dunite) and strength variation (weakening: A-/D-type → AG-type-like; strengthening: AG-type-like → B-type-like) during dynamic recrystallization. The transition of olivine CPOs from A-/D-type to B-/AG-type-like in the forearc mantle may weaken the seismic anisotropies and deviate the fast velocity direction and the fast S-wave polarization direction from trench-perpendicular to trench-oblique direction with the cooling and aging of forearc mantle. Depending on the size and distribution of the peridotite body such as the Songshugou peridotites, B- and AG-type-like olivine CPOs can be an additional (despite minor) local contributor to the orogen-parallel fast velocity direction and fast shear-wave polarization direction in the orogenic crust such as in the Songshugou area in Qinling orogen.

  18. Induced moment due to perpendicular field cycling in trained ...

    Indian Academy of Sciences (India)

    in trained exchange bias system. AMITESH PAUL1,∗ and S ... in a phenomenological picture takes the form of a unidirectional magnetic anisotropy, is known as exchange ..... [19] C V Haesendonck, private communication. Pramana – J. Phys.

  19. General multimode polarization splitter design in uniaxial media

    Science.gov (United States)

    Teixeira, Poliane A.; Silva, Daniely G.; Gabrielli, Lucas H.; Spadoti, Danilo H.; Junqueira, Mateus A. F. C.

    2018-03-01

    Quasiconformal transformation optics is used to design two-dimensional polarization beam splitters. The resulting media present inhomogeneous uniaxial permittivity and nonmagnetic response. The compact devices are theoretically designed and investigated for symmetrical and asymmetrical geometries, with footprint of 64 and 110 μm2, respectively. The polarization splitter performance is evaluated for the fundamental mode and third mode, exhibiting an insertion loss closer to 0 dB and extinction ratio above 40 dB over a broad wavelength range.

  20. Field-Induced Rheology in Uniaxial and Biaxial Fields

    International Nuclear Information System (INIS)

    MARTIN, JAMES E.

    1999-01-01

    Steady and oscillatory shear 3-D simulations of electro- and magnetorheology in uniaxial and biaxial fields are presented, and compared to the predictions of the chain model. These large scale simulations are three dimensional, and include the effect of Brownian motion. In the absence of thermal fluctuations, the expected shear thinning viscosity is observed in steady shear, and a striped phase is seen to rapidly form in a uniaxial field, with a shear slip zone in each sheet. However, as the influence of Brownian motion increases, the fluid stress decreases, especially at lower Mason numbers, and the striped phase eventually disappears, even when the fluid stress is still high. In a biaxial field, an opposite trend is seen, where Brownian motion decreases the stress most significantly at higher Mason numbers. to account for the uniaxial steady shear data they propose a microscopic chain model of the role played by thermal fluctuations on the rheology of ER and MR fluids that delineates the regimes where an applied field can impact the fluid viscosity, and gives an analytical prediction for the thermal effect. In oscillatory shear, a striped phase again appears in uniaxial field, at strain amplitudes greater than(approx) 0.15, and the presence of a shear slip zone creates strong stress nonlinearities at low strain amplitudes. In a biaxial field, a shear slip zone is not created, and so the stress nonlinearities develop only at expected strain amplitudes. The nonlinear dynamics of these systems is shown to be in good agreement with the Kinetic Chain Model

  1. Ultrasonic detection of cracks in uniaxial glass fibre rods

    CSIR Research Space (South Africa)

    Loveday, PW

    2006-01-01

    Full Text Available Conference on Computational and Applied Mechanics SACAM06 Cape Town, 16-18 January 2006 �SACAM ULTRASONIC DETECTION OF CRACKS IN UNIAXIAL GLASS FIBRE RODS Derren Wood and Philip Loveday Sensor Science and Technology, CSIR Materials Science... means of detecting internal and/or surface damage in composites which is safe, quick and relatively cost effective. Various ultrasonic techniques have been applied in the past to detect defects in composite media, the most well known being perhaps...

  2. MHD turbulence in the solar wind: evolution and anisotropy

    International Nuclear Information System (INIS)

    Horbury, T. S.; Forman, M. A.; Oughton, S.

    2005-01-01

    Spacecraft measurements in the solar wind offer the opportunity to study magnetohydrodynamic turbulence in a collisionless plasma in great detail. We review some of the key results of the study of this medium: the presence of large amplitude Alfven waves propagating predominantly away from the Sun; the existence of an active turbulent cascade; and intermittency similar to that in neutral fluids. The presence of a magnetic field leads to anisotropy of the fluctuations, which are predominantly perpendicular to this direction, as well as anisotropy of the spectrum. Some models suggest that MHD turbulence can evolve to a state with power predominantly in wave vectors either parallel to the magnetic field (slab fluctuations) or approximately perpendicular to it (2D). We present results of a new, wavelet-based analysis of magnetic field fluctuations in the solar wind, and demonstrate that the 2D component has a spectral index near the Kolmogorov value of 5/3, while slab fluctuations have a spectral index near 2. We also estimate the relative power levels in slab and 2D fluctuations, as well as the level of compressive fluctuations. Deviations of the data from the simple slab/2D model suggest the presence of power in intermediate directions and we compare our data with critical balance models. (Author)

  3. The right circular polarized waves in the three-dimensional anisotropic dispersive photonic crystals consisting of the magnetized plasma and uniaxial material as the Faraday effects considered

    International Nuclear Information System (INIS)

    Zhang, Hai-Feng; Liu, Shao-Bin; Tang, Yi-Jun; Zhen, Jian-Ping

    2014-01-01

    In this paper, the properties of the right circular polarized (RCP) waves in the three-dimensional (3D) dispersive photonic crystals (PCs) consisting of the magnetized plasma and uniaxial material with face-centered-cubic (fcc) lattices are theoretically investigated by the plane wave expansion method, which the homogeneous anisotropic dielectric spheres (the uniaxial material) immersed in the magnetized plasma background, as the Faraday effects of magnetized plasma are considered (the incidence electromagnetic wave vector is parallel to the external magnetic field at any time). The equations for calculating the anisotropic photonic band gaps (PBGs) for the RCP waves in the first irreducible Brillouin zone are theoretically deduced. The anisotropic PBGs and a flatbands region can be obtained. The effects of the ordinary-refractive index, extraordinary-refractive index, anisotropic dielectric filling factor, plasma frequency, and plasma cyclotron frequency (the external magnetic field) on the properties of first two anisotropic PBGs for the RCP waves are investigated in detail, respectively. The numerical results show that the anisotropy can open partial band gaps in fcc lattices at U and W points, and the complete PBGs for the RCP waves can be achieved compared to the conventional 3D dispersive PCs composed of the magnetized plasma and isotropic material. It is also shown that the first two anisotropic PBGs can be tuned by those parameters as mentioned above. Those PBGs can be enlarged by introducing the uniaxial material into such 3D PCs as the Faraday effects are considered

  4. Magnetic anisotropy of thin sputtered MgB2 films on MgO substrates in high magnetic fields

    Directory of Open Access Journals (Sweden)

    Savio Fabretti

    2014-03-01

    Full Text Available We investigated the magnetic anisotropy ratio of thin sputtered polycrystalline MgB2 films on MgO substrates. Using high magnetic field measurements, we estimated an anisotropy ratio of 1.35 for T = 0 K with an upper critical field of 31.74 T in the parallel case and 23.5 T in the perpendicular case. Direct measurements of a magnetic-field sweep at 4.2 K show a linear behavior, confirmed by a linear fit for magnetic fields perpendicular to the film plane. Furthermore, we observed a change of up to 12% of the anisotropy ratio in dependence of the film thickness.

  5. Tuning the electrical and optical anisotropy of a monolayer black phosphorus magnetic superlattice

    Science.gov (United States)

    Li, X. J.; Yu, J. H.; Luo, K.; Wu, Z. H.; Yang, W.

    2018-04-01

    We investigate theoretically the effects of modulated periodic perpendicular magnetic fields on the electronic states and optical absorption spectrum in monolayer black phosphorus (phosphorene). We demonstrate that different phosphorene magnetic superlattice (PMS) orientations can give rise to distinct energy spectra, i.e. tuning the intrinsic electronic anisotropy. Rashba spin-orbit coupling (RSOC) develops a spin-splitting energy dispersion in this phosphorene magnetic superlattice. Anisotropic momentum-dependent carrier distributions along/perpendicular to the magnetic strips are demonstrated. The manipulations of these exotic electronic properties by tuning superlattice geometry, magnetic field and the RSOC term are addressed systematically. Accordingly, we find bright-to-dark transitions in the ground-state electron-hole pair transition rate spectrum and the PMS orientation-dependent anisotropic optical absorption spectrum. This feature offers us a practical way of modulating the electronic anisotropy in phosphorene by magnetic superlattice configurations and detecting this modulation capability by using an optical technique.

  6. Four dimensional X-ray imaging of deformation modes in organic-rich Green River Shale retorted under uniaxial compression

    Science.gov (United States)

    Kobchenko, M.; Pluymakers, A.; Cordonnier, B.; Tairova, A.; Renard, F.

    2017-12-01

    Time-lapse imaging of fracture network development in organic-rich shales at elevated temperatures while kerogen is retorted allows characterizing the development of microfractures and the onset of primary migration. When the solid organic matter is transformed to hydrocarbons with lower molecular weight, the local pore-pressure increases and drives the propagation of hydro-fractures sub-parallel to the shale lamination. On the scale of samples of several mm size, these fractures can be described as mode I opening, where fracture walls dilate in the direction of minimal compression. However, so far experiments coupled to microtomography in situ imaging have been performed on samples where no load was imposed. Here, an external load was applied perpendicular to the sample laminations and we show that this stress state slows down, but does not stop, the propagation of fracture along bedding. Conversely, microfractures also propagate sub-perpendicular to the shale lamination, creating a percolating network in three dimensions. To monitor this process we have used a uniaxial compaction rig combined with in-situ heating from 50 to 500 deg C, while capturing three-dimensional X-ray microtomography scans at a voxel resolution of 2.2 μm; Data were acquired at beamline ID19 at the European Synchrotron Radiation Facility. In total ten time-resolved experiments were performed at different vertical loading conditions, with and without lateral passive confinement and different heating rates. At high external load the sample fails by symmetric bulging, while at lower external load the reaction-induced fracture network develops with the presence of microfractures both sub-parallel and sub-perpendicular to the bedding direction. In addition, the variation of experimental conditions allows the decoupling of the effects of the hydrocarbon decomposition reaction on the deformation process from the influence of thermal stress heating on the weakening and failure mode of immature

  7. In-plane current-driven spin-orbit torque switching in perpendicularly magnetized films with enhanced thermal tolerance

    International Nuclear Information System (INIS)

    Wu, Di; Yu, Guoqiang; Shao, Qiming; Li, Xiang; Wong, Kin L.; Wang, Kang L.; Wu, Hao; Han, Xiufeng; Zhang, Zongzhi; Khalili Amiri, Pedram

    2016-01-01

    We study spin-orbit-torque (SOT)-driven magnetization switching in perpendicularly magnetized Ta/Mo/Co_4_0Fe_4_0B_2_0 (CoFeB)/MgO films. The thermal tolerance of the perpendicular magnetic anisotropy (PMA) is enhanced, and the films sustain the PMA at annealing temperatures of up to 430 °C, due to the ultra-thin Mo layer inserted between the Ta and CoFeB layers. More importantly, the Mo insertion layer also allows for the transmission of the spin current generated in the Ta layer due to spin Hall effect, which generates a damping-like SOT and is able to switch the perpendicular magnetization. When the Ta layer is replaced by a Pt layer, i.e., in a Pt/Mo/CoFeB/MgO multilayer, the direction of the SOT-induced damping-like effective field becomes opposite because of the opposite sign of spin Hall angle in Pt, which indicates that the SOT-driven switching is dominated by the spin current generated in the Ta or Pt layer rather than the Mo layer. Quantitative characterization through harmonic measurements reveals that the large SOT effective field is preserved for high annealing temperatures. This work provides a route to applying SOT in devices requiring high temperature processing steps during the back-end-of-line processes.

  8. Experimental investigation on the fracture behaviour of black shale by acoustic emission monitoring and CT image analysis during uniaxial compression

    Science.gov (United States)

    Wang, Y.; Li, C. H.; Hu, Y. Z.

    2018-04-01

    Plenty of mechanical experiments have been done to investigate the deformation and failure characteristics of shale; however, the anisotropic failure mechanism has not been well studied. Here, laboratory Uniaxial Compressive Strength tests on cylindrical shale samples obtained by drilling at different inclinations to bedding plane were performed. The failure behaviours of the shale samples were studied by real-time acoustic emission (AE) monitoring and post-test X-ray computer tomography (CT) analysis. The experimental results suggest that the pronounced bedding planes of shale have a great influence on the mechanical properties and AE patterns. The AE counts and AE cumulative energy release curves clearly demonstrate different morphology, and the `U'-shaped curve relationship between the AE counts, AE cumulative energy release and bedding inclination was first documented. The post-test CT image analysis shows the crack patterns via 2-D image reconstructions, an index of stimulated fracture density is defined to represent the anisotropic failure mode of shale. What is more, the most striking finding is that the AE monitoring results are in good agreement with the CT analysis. The structural difference in the shale sample is the controlling factor resulting in the anisotropy of AE patterns. The pronounced bedding structure in the shale formation results in an anisotropy of elasticity, strength and AE information from which the changes in strength dominate the entire failure pattern of the shale samples.

  9. Theoretical analysis of low-energy proton and helium anisotropies in the outer heliosphere

    International Nuclear Information System (INIS)

    Forman, M.A.; McDonald, F.B.

    1982-01-01

    Analysis of the anisotropies of low-energy protons and helium near the ecliptic plane at 12 AU in 1977 reported by McDonald and Forman, in terms of the standard convection-diffusion and drift expressions, and using the observed gradients and spectral indices, shows that their mean free paths are approximately 10 AU parallel to the mean magnetic field, that k perpendicular may be substantially larger than k transverse 2 /k parallel and that these particles may be flowing radially

  10. Effect of Layering on Cracking Initiation and Propagation under Uniaxial Compression

    Science.gov (United States)

    Modiriasari, A.; Jiang, L.; Yoon, H.; Bobet, A.; Pyrak-Nolte, L. J.

    2017-12-01

    Rock anisotropy can arise from textural and structural causes both of which contribute to anisotropic strength and moduli. Rock variability makes it difficult to determine which properties dominate failure. Here, laboratory experiments were performed on 3D printed samples to examine the effect of layering on crack formation. Samples with two pre-existing coplanar flaws were fabricated using an additive 3D printing process (Projet CJP 360). Layers of gypsum (0.2 mm thick) were printed in either a horizontal (H) or a vertical (V) orientation to create prismatic samples (152.4 mm x 76.2 mm x 25.1 mm) with two 12.7 mm long coplanar flaws (19.05 mm apart) oriented at 450 with the load. Cracks were induced under uniaxial loading conditions. Digital image correlation (DIC) and acoustic emission (AE) (18 AE sensors with a frequency range of 100-450 kHz) were used to monitor crack evolution. DIC imaging of the V specimen during uniaxial compression showed that smooth cracks were initiated and propagated from the tips of the flaws parallel to the layering. Unlike the strongly bonded samples, no cracks were formed between the pre-existing flaws. The failure mechanism between the flaws was controlled by the weak bonding between the layers, and not by the coalescence of the new cracks. However, for the H specimen, failure was caused by crack coalescence between the two flaws. The new cracks exhibited a step-like roughness that was influenced by the layering in the sample. AE events were only detected when a synchronized mode was used. 3D printed samples can be effectively used to study the effect of anisotropic layering on crack initiation and propagation in a repeatable and controlled manner. Acknowledgements: Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security

  11. Compression strength perpendicular to grain of structural timber and glulam

    DEFF Research Database (Denmark)

    Damkilde, Lars; Hoffmeyer, Preben; Pedersen, Torben N.

    1998-01-01

    The characteristic strength values for compression perpendicular to grain as they appear in EN 338 (structural timber) and EN 1194 (glulam) are currently up for discussion. The present paper provides experimental results based on EN 1193 that may assist in the correct assignment of such strength...... values. The dominant failure mode of glulam specimens is shown to be fundamentally different from that of structural timber specimens. Glulam specimens often show tension perpendicular to grain failure before the compression strength value is reached. Such failure mode is not seen for structural timber....... Nonetheless test results show that the levels of characteristic compression strength perpendicular to grain are of the same order for structural timber and glulam. The values are slightly lower than those appearing in EN 1194 and less than half of those appearing in EN 338. The paper presents a numerical...

  12. Anisotropy in electromagnetic field variations and its implication for lateral inhomogeneity of the electrical conductivity structure

    Science.gov (United States)

    Honkura, Y.; Watanabe, N.; Kaneko, Y.; Oshima, S.

    1989-03-01

    Two-dimensional analyses of magnetotelluric data provide information on anisotropic response for two different polarization cases; the so-called B-polarization and E-polarization cases. Similar anisotropy should also be observed in the horizontal components of magnetic field variations. On the assumption that a reference station provides the normal magnetic field, transfer functions for the horizontal magnetic fields can be derived in a fashion similar to the impedance analysis for magnetotelluric data. We applied this method to magnetic data obtained at some observation sites in a geothermal area in Japan. Transfer functions for the horizontal magnetic fields exhibit a strong anisotropy with the preferred direction nearly perpendicular to that for the electric field. This result implies the existence of strong electric currents flowing in the direction perpendicular to the above preferred direction for the magnetic field. The present method was also applied to the horizontal components of magnetic field variations observed at the seafloor. In this case, a magnetic observatory on land was taken as the reference station, and attenuation of the amplitude of horizontal magnetic field variation was examined. Anisotropy in attenuation was then found with the preferred direction perpendicular to the axis of the Okinawa trough where the seafloor measurement was undertaken.

  13. Some design considerations for perpendicular biased ferrite tuners

    International Nuclear Information System (INIS)

    Enchevich, I.B.; Poirier, R.L.

    1994-10-01

    Recently remarkable progress has been achieved in the development of perpendicular biased ferrite tuned rf resonators for fast cycled synchrotrons. Compared with the broadly used parallel biased rf cavities they provide higher resonator quality factor Q. However when designing perpendicular biased cavities, special attention should be paid to the methods to provide eddy current suppression in the resonator walls, the ferrite nonlinearity influence, the generated heat removal, the fast self resonant frequency control. The prospective of a faster additional biasing system are discussed and conclusions are drawn. (author). 8 refs., 6 figs

  14. Some remarks about large p/sub perpendicular/ spin effects

    International Nuclear Information System (INIS)

    Field, R.D.

    1977-01-01

    A discussion of the ingredients necessary to make predictions concerning single and double spin measurements in large p/sub perpendicular to/ inclusive processes is presented. Remarks are made as to what might be expected and what might be learned from such measurements. Various models for the production of large p/sub perpendicular to/ mesons have quite different spin structure and hence can be expected to give differing predictions. However, it is not possible at this time to make quantitative calculations, and it is possible (not probable) that the interesting spin observables will be negligibly small

  15. Heterogeneous seismic anisotropy in the transition zone and uppermost lower mantle: evidence from South America, Izu-Bonin and Japan

    Science.gov (United States)

    Lynner, Colton; Long, Maureen D.

    2015-06-01

    Measurements of seismic anisotropy are commonly used to constrain deformation in the upper mantle. Observations of anisotropy at mid-mantle depths are, however, relatively sparse. In this study we probe the anisotropic structure of the mid-mantle (transition zone and uppermost lower mantle) beneath the Japan, Izu-Bonin, and South America subduction systems. We present source-side shear wave splitting measurements for direct teleseismic S phases from earthquakes deeper than 300 km that have been corrected for the effects of upper mantle anisotropy beneath the receiver. In each region, we observe consistent splitting with delay times as large as 1 s, indicating the presence of anisotropy at mid-mantle depths. Clear splitting of phases originating from depths as great as ˜600 km argues for a contribution from anisotropy in the uppermost lower mantle as well as the transition zone. Beneath Japan, fast splitting directions are perpendicular or oblique to the slab strike and do not appear to depend on the propagation direction of the waves. Beneath South America and Izu-Bonin, splitting directions vary from trench-parallel to trench-perpendicular and have an azimuthal dependence, indicating lateral heterogeneity. Our results provide evidence for the presence of laterally variable anisotropy and are indicative of variable deformation and dynamics at mid-mantle depths in the vicinity of subducting slabs.

  16. Shear bands and anisotropy of the mechanical properties of an MA2-1pch magnesium alloy after equal-channel angular pressing

    Science.gov (United States)

    Serebryany, V. N.; Khar'kova, M. A.; D'yakonov, G. S.; Kopylov, V. I.; Dobatkin, S. V.

    2017-10-01

    Effect of structure and texture on the anisotropy of the mechanical properties of the MA2-1pch magnesium alloy subjected to equal-channel angular pressing and subsequent annealing has been studied in two mutually perpendicular planes Y and X (along and across the pressing direction). The anisotropy of the mechanical properties is shown to be due to various orientations of shear bands and various types of texture inside the bands and outside them in planes X and Y.

  17. Magnetic moment and magnetocrystalline anisotropy of 3d-ion subsystem in R2T14B

    International Nuclear Information System (INIS)

    Bartashevich, M.I.; Kudrevatykh, N.V.; Andreev, A.V.; Rejmer, V.A.

    1990-01-01

    The effect of substituting cobalt for iron on the magnetic moment, magneto-crystalline anisotropy and thermal expansion of R 2 (Fe 1-x Co x ) 14 B single crystals (R=Y, Gd, 0≤x≤0.3) is investigated. The uniaxial magnetic anisotropy constant K 1 for the 3d-subsystem passes through a maximum at T=4.2 K with increasing Co concentration. For T c the temperature dependence of K 1 does not possess a positive slope. The magnetic moment of the 3d-subsystem at 4.2 K does not exhibit the maximum at intermediate concentrations observed for most R(Fe, Co)-intermetallics. An explanation is presented of the changes in the magnetic properties. It is shown that the variation of the interatomic distances on thermal expansion should not affect the magnitude of the anisotropy constant of the 3d- and R-subsystems

  18. Antiferromagnetic iridium-manganese intermediate layers for perpendicular recording media (invited)

    Science.gov (United States)

    Srinivasan, Kumar; Piramanayagam, S. N.; Sbiaa, Rachid; Kay, Yew Seng; Tan, Hang Khume; Wong, Seng Kai

    2009-04-01

    Current generation of cobalt-oxide-based perpendicular magnetic recording media uses single or dual ruthenium intermediate layers in order to grow crystallographically textured, and magnetically isolated granular media. In this work, the potential advantages of an antiferromagnetic iridium-manganese intermediate layer directly under the recording layer are highlighted. Owing to its close lattice matching with hexagonal cobalt, iridium-manganese which has the L12, or AuCu3-type crystal structure, can support the heteroepitaxial growth of the cobalt-based recording layer. In one of the media schemes described here, (111) textured iridium-manganese thin film was grown on 7.5 nm thick ruthenium layer. On the iridium-manganese as segregation layer, the Co-oxide-based magnetic recording layer showed perpendicular texture with Δθ50 below 4°, coercivity of over 4000 Oe alongside magnetic exchange decoupling, average grain sizes of 6 nm with distributions under 14%, and improved thermal stability. Measurements of the anisotropy constant did not show any significant change and even an IrMn capping layer was observed to improve the thermal stability. The possible mechanisms through which the IrMn layer could affect the thermal stability are hypothesized. The initial layers of the magnetic recording layer on IrMn segregation layers also showed exchange-decoupled and segregated grains, which is unlike that observed on Ru segregation layers. In a second media scheme, (111) textured iridium-manganese thin film was grown on a crystalline soft magnetic underlayer belonging on top of amorphous soft underlayers. In this scheme, partial pinning of the soft underlayer due to exchange-bias interaction with the IrMn layer was observed. This scheme offers the possibility to reduce the intermediate layer thickness, thus improve media writability, and with further optimization, could potentially facilitate the approach toward 1 Tbits/in.2.

  19. Planar isotropy of passive scalar turbulent mixing with a mean perpendicular gradient.

    Science.gov (United States)

    Danaila, L; Dusek, J; Le Gal, P; Anselmet, F; Brun, C; Pumir, A

    1999-08-01

    A recently proposed evolution equation [Vaienti et al., Physica D 85, 405 (1994)] for the probability density functions (PDF's) of turbulent passive scalar increments obtained under the assumptions of fully three-dimensional homogeneity and isotropy is submitted to validation using direct numerical simulation (DNS) results of the mixing of a passive scalar with a nonzero mean gradient by a homogeneous and isotropic turbulent velocity field. It is shown that this approach leads to a quantitatively correct balance between the different terms of the equation, in a plane perpendicular to the mean gradient, at small scales and at large Péclet number. A weaker assumption of homogeneity and isotropy restricted to the plane normal to the mean gradient is then considered to derive an equation describing the evolution of the PDF's as a function of the spatial scale and the scalar increments. A very good agreement between the theory and the DNS data is obtained at all scales. As a particular case of the theory, we derive a generalized form for the well-known Yaglom equation (the isotropic relation between the second-order moments for temperature increments and the third-order velocity-temperature mixed moments). This approach allows us to determine quantitatively how the integral scale properties influence the properties of mixing throughout the whole range of scales. In the simple configuration considered here, the PDF's of the scalar increments perpendicular to the mean gradient can be theoretically described once the sources of inhomogeneity and anisotropy at large scales are correctly taken into account.

  20. Effects of Transverse Magnetic Anisotropy on Current-Induced Spin Switching

    Science.gov (United States)

    Misiorny, Maciej; Barnaś, Józef

    2013-07-01

    Spin-polarized transport through bistable magnetic adatoms or single-molecule magnets (SMMs), which exhibit both uniaxial and transverse magnetic anisotropy, is considered theoretically. The main focus is on the impact of transverse anisotropy on transport characteristics and the adatom’s or SMM’s spin. In particular, we analyze the role of quantum tunneling of magnetization (QTM) in the mechanism of the current-induced spin switching, and show that the QTM phenomenon becomes revealed as resonant peaks in the average values of the molecule’s spin and in the charge current. These features appear at some resonant fields and are observable when at least one of the electrodes is ferromagnetic.

  1. Magnetic properties of magnetic liquids with iron-oxide particles - the influence of anisotropy and interactions

    DEFF Research Database (Denmark)

    Johansson, C.; Hanson, M.; Pedersen, Michael Stanley

    1997-01-01

    Magnetic liquids containing iron-oxide particles were investigated by magnetization and Mossbauer measurements. The particles were shown to be maghemite with a spontanious saturation magentization Ms = 320 kA m-1 at 200 K and a normalized high-field susceptibility x/M0 = 5.1x10-6 mkA-1, practically...... independent of temperature. Ms increases with decreasing temperature according to an effective Bloch law with an exponent larger than 1.5, as expected for fine magnetic particles. The model of magnetic particles with uniaxial anisotropy and the actual size distribution gives a consistent description...... of independent measurements of the temperature dependence of the hyperfine field and the isothermal magnetization versus field. From this an effective anisotropy constant of about 4.5x10 4 J m-3 is estimated for a particle with diameter 7.5 nm. The magnetic relaxation, as observed in zero...

  2. Condition For Strain-Hardening In Ecc Uniaxial Test Specimen

    DEFF Research Database (Denmark)

    Dick-Nielsen, Lars; Stang, Henrik; Poulsen, Peter Noe

    2006-01-01

    and infinite sheets under uniaxial tension. The crack is assumed to be cohesive and the cohesive law applied takes into account fiber as well as mortar properties. It is shown that the maximum crack opening observed during crack propagation in various test specimen geometries is small, 20 m and also small......This paper discusses the adequateness of the steady state flat crack criterion for crack propagation in Engineered Cementitious Composites. The investigation is performed by use of a semi-analytical model as well as a Finite Element Model. The simulations are for one crack propagating in finite...

  3. Domain shape instabilities and dendrite domain growth in uniaxial ferroelectrics

    Science.gov (United States)

    Shur, Vladimir Ya.; Akhmatkhanov, Andrey R.

    2018-01-01

    The effects of domain wall shape instabilities and the formation of nanodomains in front of moving walls obtained in various uniaxial ferroelectrics are discussed. Special attention is paid to the formation of self-assembled nanoscale and dendrite domain structures under highly non-equilibrium switching conditions. All obtained results are considered in the framework of the unified kinetic approach to domain structure evolution based on the analogy with first-order phase transformation. This article is part of the theme issue `From atomistic interfaces to dendritic patterns'.

  4. Uniaxial compression tests on diesel contaminated frozen silty soil specimens

    International Nuclear Information System (INIS)

    Chenaf, D.; Stampli, N.; Bathurst, R.; Chapuis, R.P.

    1999-01-01

    Results of a uniaxial, unconfined compression test on artificial diesel-contaminated and uncontaminated frozen silty soils are discussed. The testing program involved 59 specimens. The results show that for the same fluid content, diesel contamination reduced the strength of the frozen specimens by increasing the unfrozen water content. For example, in specimens containing 50 per cent diesel oil of the fluid content by weight the maximum strength was reduced by 95 per cent compared to the strength of an uncontaminated specimen. Diesel contamination was also shown to contribute to the slippage between soil particles by acting as a lubricant, thus accelerating the loss of compressive strength.13 refs., 18 figs

  5. Time Dependent and Steady Uni-axial Elongational Viscosity

    DEFF Research Database (Denmark)

    Nielsen, Jens K.; Rasmussen, Henrik Koblitz; Hassager, Ole

    2005-01-01

    Here we present measurements of transient and steady uni-axial elongational viscosity, using the Filament Stretching Rheometer1 or FSR1 (see Fig. 1) of the following melts: Four narrow MMD polystyrene (PS) samples with weight-average molar mass Mw in the range of 50k to 390k. Three different bi......-disperse samples, mixed from the narrow MMD PS. Two low-density polyethylene (LDPE) melts (Lupolen 1840D and 3020D). A steady-state viscosity was kept for 1-2.5 Hencky strain units in all measurements....

  6. Origin and spectroscopic determination of trigonal anisotropy in a heteronuclear single-molecule magnet

    Science.gov (United States)

    Sorace, L.; Boulon, M.-E.; Totaro, P.; Cornia, A.; Fernandes-Soares, J.; Sessoli, R.

    2013-09-01

    W-band (ν ≅ 94 GHz) electron paramagnetic resonance (EPR) spectroscopy was used for a single-crystal study of a star-shaped Fe3Cr single-molecule magnet (SMM) with crystallographically imposed trigonal symmetry. The high resolution and sensitivity accessible with W-band EPR allowed us to determine accurately the axial zero-field splitting terms for the ground (S = 6) and first two excited states (S = 5 and S = 4). Furthermore, spectra recorded by applying the magnetic field perpendicular to the trigonal axis showed a π/6 angular modulation. This behavior is a signature of the presence of trigonal transverse magnetic anisotropy terms whose values had not been spectroscopically determined in any SMM prior to this work. Such in-plane anisotropy could only be justified by dropping the so-called “giant spin approach” and by considering a complete multispin approach. From a detailed analysis of experimental data with the two models, it emerged that the observed trigonal anisotropy directly reflects the structural features of the cluster, i.e., the relative orientation of single-ion anisotropy tensors and the angular modulation of single-ion anisotropy components in the hard plane of the cluster. Finally, since high-order transverse anisotropy is pivotal in determining the spin dynamics in the quantum tunneling regime, we have compared the angular dependence of the tunnel splitting predicted by the two models upon application of a transverse field (Berry-phase interference).

  7. PLT and PDX perpendicular charge-exchange analyzers

    International Nuclear Information System (INIS)

    Mueller, D.; Hammett, G.W.; McCune, D.C.

    1986-01-01

    The perpendicular charge-exchange systems used on the poloidal divertor experiment and the Princeton large torus are comprised of ten-channel, mass-resolved, charge-exchange analyzers. Results from these systems indicate that instrumental effects can lead to erroneous temperature measurements during deuterium neutral beam injection or at low hydrogen concentrations

  8. Timber beams loaded perpendicular to grain by multiple connections

    NARCIS (Netherlands)

    Leijten, A.J.M.; Schoenmakers, J.C.M.

    2014-01-01

    In timber structures, beams which are loaded perpendicular to grain by connections along the span may fail by splitting, resulting in the collapse of the beam. In the past, empirical, semi-empirical and fracture mechanical models have been developed aiming at predicting the splitting failure load.

  9. Streamer discharges can move perpendicularly to the electric field

    NARCIS (Netherlands)

    Nijdam, S.; Takahashi, E.; Teunissen, J.; Ebert, U.

    2014-01-01

    Streamer discharges are a primary mode of electric breakdown in thunderstorms and high voltage technology; they are generally believed to grow along electric field lines. However, we here give experimental and numerical evidence that streamers can propagate nearly perpendicularly to the background

  10. Pressure anisotropy and radial stress balance in the Jovian neutral sheet

    Science.gov (United States)

    Paranicas, C. P.; Mauk, B. H.; Krimigis, S. M.

    1991-01-01

    By examining particle and magnetic field data from the Voyager 1 and 2 spacecraft, signatures were found indicating that the (greater than about 28 keV) particle pressure parallel to the magnetic field is greater than the pressure perpendicular to the field within the nightside neutral sheet (three nightside neutral sheet crossings, with favorable experimental conditions, were used). By incorporating the pressure anisotropy into the calculation of radial forces within the hightside neutral sheet, it is found that (1) force balance is approximately achieved and (2) the anisotropy force term provides the largest contribution of the other particle forces considered (pressure gradients and the corotation centrifugal force). With regard to the problem of understanding the balance of radial forces within the dayside neutral sheet (McNutt, 1984; Mauk and Krimigis, 1987), the nightside pressure anisotropy force is larger than the dayside pressure gradient forces at equivalent radial distances; however, a full accounting of the dayside regions remains to be achieved.

  11. Development and anisotropy of three-dimensional turbulence in a current sheet

    International Nuclear Information System (INIS)

    Onofri, M.; Veltri, P.; Malara, F.

    2007-01-01

    The nonlinear evolution of three-dimensional reconnection instabilities are studied in a current sheet where many resonant surfaces are simultaneously present at different locations of the simulation domain. The nonlinear evolution produces the development of anisotropic magnetohydrodynamic turbulence. The development of the energy spectrum is followed until the energy is transported to the dissipative length scale and the anisotropy of the spectrum is analyzed. The energy cascade is affected by the Alfven effect and it takes place mainly in the direction perpendicular to the local average magnetic field. Anisotropy is also affected by propagation of perturbations across the main magnetic field, due to the growth of a transverse component related to reconnection. The direction of anisotropy varies with the position in space. The spectral index is different both from what is found in homogeneous isotropic turbulence and from the values predicted for magnetohydrodynamic turbulence with a uniform large-scale magnetic field

  12. Development of a tensile-stress-induced anisotropy in amorphous magnetic thin films

    International Nuclear Information System (INIS)

    Mandal, K.; Vazquez, M.; Garcia, D.; Castano, F.J.; Prados, C.; Hernando, A.

    2000-01-01

    Magnetic anisotropy was induced in positive magnetostrictive Fe 80 B 20 and negative magnetostrictive Co 75 Si 15 B 10 thin films by developing a tensile stress within the samples. The films were grown on the concave surfaces of mechanically bowed glass substrates. On releasing the substrates from the substrate holders, a tensile stress was developed within the samples that modified the domain structure. As a result of it, a magnetic easy axis parallel to the direction of the stress was induced in FeB sample whereas in CoSiB sample the induced easy axis was perpendicular to the direction of the developed stress. To produce magnetic multilayers with crossed anisotropy, FeB/CoSiB bilayers and FeB/Cu/CoSiB trilayers were grown on bowed substrates. The study of magnetic properties of the multilayers indicates the development of crossed anisotropy within them, particularly when the magnetic layers are separated by a nonmagnetic Cu layer

  13. Effect of anisotropy on anomalous Hall effect in Tb-Fe thin films

    International Nuclear Information System (INIS)

    Babu, V. Hari; Markandeyulu, G.; Subrahmanyam, A.

    2009-01-01

    The electrical and Hall resistivities of Tb x Fe 100-x thin films in the temperature range 13-300 K were investigated. The sign of Hall resistivity at 300 K is found to change from positive for x=28 film to negative for x=30 film, in accordance with the compensation of Tb and Fe moments. All the films are seen to have planar magnetic anisotropy at 13 K. The temperature coefficients of electrical resistivities of the amorphous films with 19≤x≤51 are seen to be negative. The temperature dependence of Hall resistivity of these films is explained on the basis of random magnetic anisotropy model. The temperature dependences of Hall resistivities of the x=22 and 41 films are seen to exhibit a nonmonotonous behavior due to change in anisotropy from perpendicular to planar. The same behavior is considered for the explanation regarding the probable formation of Berry phase curvature in these films.

  14. Preliminary results of characteristic seismic anisotropy beneath Sunda-Banda subduction-collision zone

    Energy Technology Data Exchange (ETDEWEB)

    Wiyono, Samsul H., E-mail: samsul.wiyono@bmkg.go.id [Study Program of Earth Sciences, Faculty of Earth Sciences and Technology, Institute of Technology Bandung, Bandung 40132 (Indonesia); Indonesia’s Agency for Meteorology Climatology and Geophysics, Jakarta 10610 (Indonesia); Nugraha, Andri Dian, E-mail: nugraha@gf.itb.ac.id [Indonesia’s Agency for Meteorology Climatology and Geophysics, Jakarta 10610 (Indonesia); Global Geophysics Research Group, Faculty of Mining and Petroleum Engineering, Institute of Technology Bandung, Bandung 40132, Indonesia, Phone: +62-22 2534137 (Indonesia)

    2015-04-24

    Determining of seismic anisotropy allowed us for understanding the deformation processes that occured in the past and present. In this study, we performed shear wave splitting to characterize seismic anisotropy beneath Sunda-Banda subduction-collision zone. For about 1,610 XKS waveforms from INATEWS-BMKG networks have been analyzed. From its measurements showed that fast polarization direction is consistent with trench-perpendicular orientation but several stations presented different orientation. We also compared between fast polarization direction with absolute plate motion in the no net rotation and hotspot frame. Its result showed that both absolute plate motion frame had strong correlation with fast polarization direction. Strong correlation between the fast polarization direction and the absolute plate motion can be interpreted as the possibility of dominant anisotropy is in the asthenosphere.

  15. Effect of anisotropy on the magnon energy gap in a two-layer ferromagnetic superlattice

    International Nuclear Information System (INIS)

    Qiu Rongke; Liang Jing; Li Qingfeng; Zhang Zhidong; Song Panpan; Hong Xiaomin

    2009-01-01

    The magnon energy bands or spectra in a two-layer ferromagnetic superlattice are studied. It is found that a modulated energy gap exists in the magnon energy band along K x direction perpendicular to the superlattice plane, which is different from the optical magnon gap at K x =0. The anisotropy, the spin quantum numbers and the interlayer exchange couplings all affect the magnon energy gap. If the anisotropy exists, there will be no acoustic energy branch in the system. There is a competition effect of the anisotropy and the spin quantum number on the magnon energy gap. The competition achieves a balance at the zero energy gap, at which the symmetry of the system is higher. The two energy spectra of the two-layer ferromagnetic superlattice are lowered with increasing temperature.

  16. Field driven ferromagnetic phase nucleation and propagation from the domain boundaries in antiferromagnetically coupled perpendicular anisotropy films

    Energy Technology Data Exchange (ETDEWEB)

    Hauet, Thomas; Gunther, Christian M.; Hovorka, Ondrej; Berger, Andreas; Im, Mi-Young; Fischer, Peter; Hellwig, Olav

    2008-12-09

    We investigate the reversal process in antiferromagnetically coupled [Co/Pt]{sub X-1}/{l_brace}Co/Ru/[Co/Pt]{sub X-1}{r_brace}{sub 16} multilayer films by combining magnetometry and Magnetic soft X-ray Transmission Microscopy (MXTM). After out-of-plane demagnetization, a stable one dimensional ferromagnetic (FM) stripe domain phase (tiger-tail phase) for a thick stack sample (X=7 is obtained), while metastable sharp antiferromagnetic (AF) domain walls are observed in the remanent state for a thinner stack sample (X=6). When applying an external magnetic field the sharp domain walls of the thinner stack sample transform at a certain threshold field into the FM stripe domain wall phase. We present magnetic energy calculations that reveal the underlying energetics driving the overall reversal mechanisms.

  17. Coercivity and induced magnetic anisotropy by stress and/or field annealing in Fe- and Co- based (Finemet-type) amorphous alloys

    International Nuclear Information System (INIS)

    Miguel, C.; Zhukov, A.; Val, J.J. del; Gonzalez, J.

    2005-01-01

    Uniaxial magnetic anisotropy has been induced in amorphous Fe 73.5 Cu 1 Nb 3 Si 15.5 B 7 (Fe-rich) and (Co 77 Si 13.5 B 9.5 ) 90 Fe 7 Nb 3 (Co-rich) ferromagnetic alloys by annealing under stress and/or magnetic field. Such anisotropy plays a crucial role on the magnetization process and, consequently, determine the future applications of these materials. The mechanisms involved on the origin of such induced magnetic anisotropy showed significant differences between Fe-rich and Co-rich amorphous alloys. This work provides a comparative study of the coercive field and induced magnetic anisotropy in Fe-rich and Co-rich (Finemet) amorphous alloys treated by stress and/or field

  18. Variable substrate temperature deposition of CoFeB film on Ta for manipulating the perpendicular coercive forces

    Energy Technology Data Exchange (ETDEWEB)

    Lakshmanan, Saravanan; Rao, Subha Krishna [Nanotechnology Research Centre, SRM University, Kattankulathur, Chennai 603203 (India); Muthuvel, Manivel Raja [Defence Metallurgical Research Laboratory (DMRL), Hyderabad 500058 (India); Chandrasekaran, Gopalakrishnan [Nanotechnology Research Centre, SRM University, Kattankulathur, Chennai 603203 (India); Therese, Helen Annal, E-mail: helen.a@ktr.srmuniv.ac.in [Nanotechnology Research Centre, SRM University, Kattankulathur, Chennai 603203 (India)

    2017-08-01

    Highlights: • Ta/CoFeB(50 nm)/Ta thin films were deposited at various substrate temperatures (T{sub s}). • CoFeB films deposited at T{sub s} such as RT, 450 °C, 475 °C and 500 °C exhibited perpendicular coercivity. • CoFeB deposited at 475 °C displayed a higher coercivity of 315 Oe and a low M{sub s} of 169 emu/cc. • The enhanced crystallization of CoFeB at the Ta/CoFeB interface results in higher H{sub c} (⟂). - Abstract: Magnetization of Ta/CoFeB/Ta trilayer films with thick layer of CoFeB deposited under different substrate temperatures (T{sub s}) via ultra-high vacuum DC sputtering technique has been measured with the applied magnetic field parallel and perpendicular to the plane of the film respectively to study the perpendicular coercive forces of the film. The samples were further analyzed for its structural, topological, morphological, and electrical transport properties. The core chemical states for the elements present in the CoFeB thin film were analyzed by XPS studies. Magnetization studies reveal the existence of perpendicular coercive forces in CoFeB films deposited only at certain temperatures such as RT, 450 °C, 475 °C and 500 °C. CoFeB film deposited at 475 °C exhibited a maximum coercivity of 315 Oe and a very low saturation magnetization (M{sub s}) of 169 emu/cc in perpendicular direction. This pronounced effect in perpendicular coercive forces observed for CoFeB475 could be attributed to the effect of temperature in enhancing the crystallization of the film at the Ta/CoFeB interfaces. However at temperatures higher than 475 °C the destruction of the Ta/CoFeB interface due to intermixing of Ta and CoFeB results in the disappearance of magnetic anisotropy.

  19. Raman study of lead zirconate titanate under uniaxial stress

    International Nuclear Information System (INIS)

    Tallant, David R.; Simpson, Regina L.; Grazier, J. Mark; Zeuch, David H.; Olson, Walter R.; Tuttle, Bruce A.

    2000-01-01

    The authors used micro-Raman spectroscopy to monitor the ferroelectric (FE) to antiferroelectric (AFE) phase transition in PZT ceramic bars during the application of uniaxial stress. They designed and constructed a simple loading device, which can apply sufficient uniaxial force to transform reasonably large ceramic bars while being small enough to fit on the mechanical stage of the microscope used for Raman analysis. Raman spectra of individual grains in ceramic PZT bars were obtained as the stress on the bar was increased in increments. At the same time gauges attached to the PZT bar recorded axial and lateral strains induced by the applied stress. The Raman spectra were used to calculate an FE coordinate, which is related to the fraction of FE phase present. The authors present data showing changes in the FE coordinates of individual PZT grains and correlate these changes to stress-strain data, which plot the macroscopic evolution of the FE-to-AFE transformation. Their data indicates that the FE-to-AFE transformation does not occur simultaneously for all PZT grains but that grains react individually to local conditions

  20. Uniaxial ratcheting behavior of sintered nanosilver joint for electronic packaging

    International Nuclear Information System (INIS)

    Chen, Gang; Yu, Lin; Mei, Yunhui; Li, Xin; Chen, Xu; Lu, Guo-Quan

    2014-01-01

    Uniaxial ratcheting behavior and the fatigue life of sintered nanosilver joint were investigated at room temperature. All tests were carried out under stress-controlled mode. Force–displacement data were recorded during the entire fatigue lifespan by a non-contact displacement detecting system. Effects of stress amplitude, mean stress, stress rate, and stress ratio on the uniaxial ratcheting behavior of the sintered nanosilver joint were discussed. Stress-life (S–N) curves of the sintered joints were also obtained. The Smith–Watson–Topper (SWT) model, the Gerber model and the modified Goodman model, all of which took effect of mean stress into consideration, were compared for predicting the fatigue life of the sintered joint. Both the ratcheting strain and its rate increased with increasing stress amplitude or mean stress. The increase in stress amplitude and mean stress both reduced the fatigue life of the sintered joint, while the fatigue life prolonged with the increase in stress rate and stress ratio. The modified Goodman model predicted the fatigue life of the sintered joints well

  1. Feasibilty of a Multi-bit Cell Perpendicular Magnetic Tunnel Junction Device

    Science.gov (United States)

    Kim, Chang Soo

    deposition because the high sputtering power can degrade perpendicular magnetic anisotropy of the bottom L1 0 FePt film and also increase RMS film surface roughness of the MgO tunnel barrier layer. From a lithographically unpatterned PMTJ sample, MR ratio and RA were measured at room temperature by the CIPT method and found to be 138% and 6.4 kOmicrom2, respectively. A completed PMTJ test pattern with a junction size of 80x40 microm2 was fabricated and showed a measured MR ratio and RA product of 108% and 4~6 kOmicrom 2, respectively. These values agree relatively well with the corresponding values of 138% and 6.4 kOmicrom2 obtained from the unpatterned PMTJ sample measured by a current-in-plane tunneling (CIPT) method.

  2. Exchange anisotropy and micromagnetic properties of PtMn/NiFe bilayers

    International Nuclear Information System (INIS)

    Pokhil, Taras; Linville, Eric; Mao, Sining

    2001-01-01

    Magnetic microstructure, exchange induced uniaxial and unidirectional anisotropy and structural transformation have been studied in PtMn/NiFe bilayer films and small elements as a function of annealing time. The relationship between the fcc-fct ordering phase transformation in PtMn and the development of exchange induced magnetic properties in PtMn/NiFe bilayers is complicated by the fact that the transformation occurs throughout the entire volume of the PtMn film, while the exchange between the layers is predominantly an interface effect. Consequently, the development of the exchange anisotropy should depend primarily on the character of the structural transformation at the interface between PtMn and NiFe. The purpose of this article is to correlate the volume phase transformation in PtMn to the development of exchange anisotropy and micromagnetic behavior in PtMn/NiFe bilayers. The interface structure can be inferred from the anisotropy and micromagnetic measurements, leading to a model that explains the relationship between the volume and interface transformation structures in PtMn, and magnetic properties of the bilayers. The structure and magnetic properties were characterized by x-ray diffraction, vibrating sample magnetometry, and magnetic force microscopy. [copyright] 2001 American Institute of Physics

  3. Stress induced anisotropy in CoFeMn soft magnetic nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Leary, A. M., E-mail: leary@cmu.edu; Keylin, V.; McHenry, M. E. [Materials Science and Engineering Department, Carnegie Mellon University, 5000 Forbes Ave., Pittsburgh, Pennsylvania 15213 (United States); Ohodnicki, P. R. [Functional Materials Development Division, National Energy Technology Laboratory (NETL), 626 Cochrans Mill Road, Pittsburgh, Pennsylvania 15236 (United States)

    2015-05-07

    The use of processing techniques to create magnetic anisotropy in soft magnetic materials is a well-known method to control permeability and losses. In nanocomposite materials, field annealing below the Curie temperature results in uniaxial anisotropy energies up to ∼2 kJ/m{sup 3}. Higher anisotropies up to ∼10 kJ/m{sup 3} result after annealing Fe-Si compositions under stress due to residual stress in the amorphous matrix acting on body centered cubic crystals. This work describes near zero magnetostriction Co{sub 80−x−y}Fe{sub x}Mn{sub y}Nb{sub 4}B{sub 14}Si{sub 2} soft magnetic nanocomposites, where x and y < 8 at.% with close packed crystalline grains that show stress induced anisotropies up to ∼50 kJ/m{sup 3} and improved mechanical properties with respect to Fe-Si compositions. Difference patterns measured using transmission X-ray diffraction show evidence of affine strain with respect to the stress axis.

  4. Anisotropy in the deep Earth

    Science.gov (United States)

    Romanowicz, Barbara; Wenk, Hans-Rudolf

    2017-08-01

    Seismic anisotropy has been found in many regions of the Earth's interior. Its presence in the Earth's crust has been known since the 19th century, and is due in part to the alignment of anisotropic crystals in rocks, and in part to patterns in the distribution of fractures and pores. In the upper mantle, seismic anisotropy was discovered 50 years ago, and can be attributed for the most part, to the alignment of intrinsically anisotropic olivine crystals during large scale deformation associated with convection. There is some indication for anisotropy in the transition zone, particularly in the vicinity of subducted slabs. Here we focus on the deep Earth - the lower mantle and core, where anisotropy is not yet mapped in detail, nor is there consensus on its origin. Most of the lower mantle appears largely isotropic, except in the last 200-300 km, in the D″ region, where evidence for seismic anisotropy has been accumulating since the late 1980s, mostly from shear wave splitting measurements. Recently, a picture has been emerging, where strong anisotropy is associated with high shear velocities at the edges of the large low shear velocity provinces (LLSVPs) in the central Pacific and under Africa. These observations are consistent with being due to the presence of highly anisotropic MgSiO3 post-perovskite crystals, aligned during the deformation of slabs impinging on the core-mantle boundary, and upwelling flow within the LLSVPs. We also discuss mineral physics aspects such as ultrahigh pressure deformation experiments, first principles calculations to obtain information about elastic properties, and derivation of dislocation activity based on bonding characteristics. Polycrystal plasticity simulations can predict anisotropy but models are still highly idealized and neglect the complex microstructure of polyphase aggregates with strong and weak components. A promising direction for future progress in understanding the origin of seismic anisotropy in the deep mantle

  5. Surface energy anisotropy of tungsten

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, R; Grenga, H E [Georgia Inst. of Tech., Atlanta (USA). School of Chemical Engineering

    1976-10-01

    Field-ion microscopy was used to study the faceting behavior and/or surface energy anisotropy of tungsten in vacuum and in hydrogen. In vacuum below 1700 K the activation energy for (110) facet growth agreed with values previously reported for surface diffusion on tungsten. The observed anisotropy values at 0.5 Tsub(m), where Tsub(m) is the absolute melting temperature of tungsten (approximately 3680 K), were different from those previously reported at higher temperatures and more nearly agreed with broken bond calculations based on Mie potential using m=5, n=8, and a 1.5% lattice expansion. Hydrogen appeared to have a negligible effect on surface energy anisotropy, but did preferentially increase surface diffusion rates on (310) regions.

  6. Ultrahigh Tunneling-Magnetoresistance Ratios in Nitride-Based Perpendicular Magnetic Tunnel Junctions from First Principles

    Science.gov (United States)

    Yang, Baishun; Tao, Lingling; Jiang, Leina; Chen, Weizhao; Tang, Ping; Yan, Yu; Han, Xiufeng

    2018-05-01

    We report a first-principles study of electronic structures, magnetic properties, and the tunneling-magnetoresistance (TMR) effect of a series of ferromagnetic nitride M4N (M =Fe , Co, Ni)-based magnetic tunnel junctions (MTJs). It is found that bulk Fe4 N reveals a half-metal nature in terms of the Δ1 state. A perpendicular magnetic anisotropy is observed in the periodic system Fe4 N /MgO . In particular, the ultrahigh TMR ratio of over 24 000% is predicted in the Fe4 N /MgO /Fe4N MTJ due to the interface resonance tunneling and relatively high transmission for states of other symmetry. Besides, the large TMR can be maintained with the change of atomic details at the interface, such as the order-disorder interface, the change of thickness of the MgO barrier, and different in-plane lattice constants of the MTJ. The physical origin of the TMR effect can be well understood by analyzing the band structure and transmission channel of bulk Fe4 N as well as the transmission in momentum space of Fe4 N /MgO /Fe4N . Our results suggest that the Fe4 N /MgO /Fe4N MTJ is a benefit for spintronic applications.

  7. Tunable anomalous hall effect induced by interfacial catalyst in perpendicular multilayers

    Science.gov (United States)

    Zhang, J. Y.; Peng, W. L.; Sun, Q. Y.; Liu, Y. W.; Dong, B. W.; Zheng, X. Q.; Yu, G. H.; Wang, C.; Zhao, Y. C.; Wang, S. G.

    2018-04-01

    The interfacial structures, playing a critical role on the transport properties and the perpendicular magnetic anisotropy in thin films and multilayers, can be modified by inserting an ultrathin functional layer at the various interfaces. The anomalous Hall effect (AHE) in the multilayers with core structure of Ta/CoFeB/X/MgO/Ta (X: Hf or Pt) is tuned by interfacial catalytic engineering. The saturation anomalous Hall resistance (RAH) is increased by 16.5% with 0.1 nm Hf insertion compared with the reference sample without insertion. However, the RAH value is decreased by 9.0% with 0.1 nm Pt insertion. The interfacial states were characterized by the X-ray photoelectron spectroscopy (XPS). The XPS results indicate that a strong bonding between Hf and O for Hf insertion, but no bonding between Pt and O for Pt insertion. The bonding between metal and oxygen leads to various oxygen migration behavior at the interfaces. Therefore, the opposite behavior about the RAH originates from the different oxygen behavior due to various interfacial insertion. This work provides a new approach to manipulate spin transport property for the potential applications.

  8. Electric-field control of magnetic domain-wall velocity in ultrathin cobalt with perpendicular magnetization.

    Science.gov (United States)

    Chiba, D; Kawaguchi, M; Fukami, S; Ishiwata, N; Shimamura, K; Kobayashi, K; Ono, T

    2012-06-06

    Controlling the displacement of a magnetic domain wall is potentially useful for information processing in magnetic non-volatile memories and logic devices. A magnetic domain wall can be moved by applying an external magnetic field and/or electric current, and its velocity depends on their magnitudes. Here we show that the applying an electric field can change the velocity of a magnetic domain wall significantly. A field-effect device, consisting of a top-gate electrode, a dielectric insulator layer, and a wire-shaped ferromagnetic Co/Pt thin layer with perpendicular anisotropy, was used to observe it in a finite magnetic field. We found that the application of the electric fields in the range of ± 2-3 MV cm(-1) can change the magnetic domain wall velocity in its creep regime (10(6)-10(3) m s(-1)) by more than an order of magnitude. This significant change is due to electrical modulation of the energy barrier for the magnetic domain wall motion.

  9. Quantifying the effects of disorder on switching of perpendicular spin ice arrays

    Science.gov (United States)

    Kempinger, Susan; Fraleigh, Robert; Lammert, Paul; Crespi, Vincent; Samarth, Nitin; Zhang, Sheng; Schiffer, Peter

    There is much contemporary interest in probing custom designed, frustrated systems such as artificial spin ice. To that end, we study arrays of lithographically patterned, single-domain Pt/Co multilayer islands. Due to the perpendicular anisotropy of these materials, we are able to use diffraction-limited magneto-optical Kerr effect microscopy to access the magnetic state in situ with an applied field. As we tune the interaction strength by adjusting the lattice spacing, we observe the switching field distribution broadening with increasing dipolar interactions. Using a simple mathematical analysis we extract the intrinsic disorder (the disorder that would be present without interactions) from these switching field distributions. We also characterize the intrinsic disorder by systematically removing neighbor effects from the switching field distribution. Understanding this disorder contribution as well as the interaction strength allows us to more accurately characterize the moment correlation. This project was funded by the US Department of Energy, Office of Basic Energy Sciences, Materials Sciences and Engineering Division under Grant No. DE- SC0010778

  10. Momentum anisotropy at freeze out

    International Nuclear Information System (INIS)

    Feld, S.; Borghini, N.; Lang, C.

    2017-01-01

    The transition from a hydrodynamical modeling to a particle-based approach is a crucial element of the description of high-energy heavy-ion collisions. Assuming this “freeze out” happens instantaneously at each point of the expanding medium, we show that the local phase-space distribution of the emitted particles is asymmetric in momentum space. This suggests the use of anisotropic hydrodynamics for the last stages of the fluid evolution. We discuss how observables depend on the amount of momentum-space anisotropy at freeze out and how smaller or larger anisotropies allow for different values of the freeze-out temperature. (paper)

  11. Highly tunable perpendicularly magnetized synthetic antiferromagnets for biotechnology applications

    OpenAIRE

    Vemulkar, T; Mansell, Rhodri; Petit, Dorothee Celine; Cowburn, Russell Paul; Lesniak, MS

    2015-01-01

    Magnetic micro and nanoparticles are increasingly used in biotechnological applications due to the ability to control their behavior through an externally applied field. We demonstrate the fabrication of particles made from ultrathin perpendicularly magnetized CoFeB/Pt layers with antiferromagnetic interlayer coupling. The particles are characterized by zero moment at remanence, low susceptibility at low fields, and a large saturated moment created by the stacking of the basic coupled bilayer...

  12. Plagioclase-dominated Seismic Anisotropy in the Basin and Range Lower Crust

    Science.gov (United States)

    Bernard, R. E.; Behr, W. M.

    2017-12-01

    Observations of seismic anisotropy have the ability to provide important information on deformation and structures within the lithosphere. While the mechanisms controlling seismic anisotropy in the upper mantle are fairly well understood (i.e., olivine "lattice preferred orientation" or LPO), less is known about the minerals and structures controlling regional lower crustal anisotropy. We use lower crustal xenoliths from young cinder cones in the eastern Mojave/western Basin and Range to investigate mineral LPOs and their effect on seismic anisotropy. Lower crustal gabbros were collected from two areas roughly 80 km apart — the Cima and Deadman Lake Volcanic Fields. Lower crustal fabrics measured using EBSD are dominated by LPOs in plagioclase associated with both plastic deformation and magmatic flow. In all fabric types, plagioclase LPOs produce seismic fast axes oriented perpendicular to the foliation plane. This is in contrast to mantle peridotite xenoliths from the same locations, which preserve olivine LPOs with fast axes aligned parallel to the foliation plane. The orthogonal orientations of mantle and lower crustal fast axes relative to foliation implies that even where fabric development in both layers is coeval and kinematically compatible, their measured anisotropies can be perpendicular to each other, therefore appearing anti-correlated when measured seismically. Furthermore, our observation of plagioclase-dominated LPO and negligible concentrations of mica is at odds with the common assumption that lower crustal anisotropy is dominated by micaceous minerals, whose slow axes reliably align parallel to lineation or flow. In contrast, our data show that for plagioclase, fast axes align perpendicular to flow and the slow axes are variably aligned within the foliation plane. Therefore, for a crustal section dominated by plagioclase LPO with assumed horizontal foliation, there would be a vertical rather than a horizontal axis of symmetry, resulting in a

  13. Magneto-optical measurement of anisotropy energy constant(s) for amorphous rare earth, transition metal alloys

    International Nuclear Information System (INIS)

    Uber, R.E.; Mansuripur, M.

    1988-01-01

    Optical investigation of magneto-optical films is complementary to conventional torque and VSM magnetometry. In the authors' laboratory, they are now measuring anisotropy energy constants of RE-TM thin films at temperatures from ambient to 150 0 C. An in-plane magnetic field (up to 16.5 KOe) is applied to a saturated sample with perpendicular magnetization. The movement away from the perpendicular direction is monitored using the polar Kerr effect. At the HeNe wavelength, the Kerr effect is principally due to the top 500 angstroms of the transition metal subnetwork in the films

  14. Exchange bias in nearly perpendicularly coupled ferromagnetic/ferromagnetic system

    International Nuclear Information System (INIS)

    Bu, K.M.; Kwon, H.Y.; Oh, S.W.; Won, C.

    2012-01-01

    Exchange bias phenomena appear not only in ferromagnetic/antiferromagnetic systems but also in ferromagnetic/ferromagnetic systems in which two layers are nearly perpendicularly coupled. We investigated the origin of the symmetry-breaking mechanism and the relationship between the exchange bias and the system's energy parameters. We compared the results of computational Monte Carlo simulations with those of theoretical model calculation. We found that the exchange bias exhibited nonlinear behaviors, including sign reversal and singularities. These complicated behaviors were caused by two distinct magnetization processes depending on the interlayer coupling strength. The exchange bias reached a maximum at the transition between the two magnetization processes. - Highlights: ► Exchange bias phenomena are found in perpendicularly coupled F/F systems. ► Exchange bias exhibits nonlinear behaviors, including sign reversal and singularities. ► These complicated behaviors were caused by two distinct magnetization processes. ► Exchange bias reached a maximum at the transition between the two magnetization processes. ► We established an equation to maximize the exchange bias in perpendicularly coupled F/F system.

  15. Double-layered perpendicular magnetic recording media of granular-type FePt-MgO films

    International Nuclear Information System (INIS)

    Zhang Zhengang; Singh, Amarendra K.; Yin Jinhua; Perumal, A.; Suzuki, Takao

    2005-01-01

    The recording performance of double-layered granular-type FePt-MgO perpendicular magnetic recording media fabricated onto glass discs by sputtering is investigated. The (0 0 1)-textured FePt granular films are obtained by annealing FePt/MgO multilayers. Three different multilayer structures are compared in their magnetic properties and recording SNR performances. To evaluate thermal stability property of these granular-type FePt disks, the time-dependent magnetic force microscope (MFM) signal from the written bits on one of these disks is recorded in the temperature range 25-200 degree sign C. The signal decay at high observation temperature is interpreted based on the temperature dependence of magnetic anisotropy (K u )

  16. Interplay of Rashba effect and spin Hall effect in perpendicular Pt/Co/MgO magnetic multilayers

    Institute of Scientific and Technical Information of China (English)

    赵云驰; 杨光; 董博闻; 王守国; 王超; 孙阳; 张静言; 于广华

    2016-01-01

    The interplay of the Rashba effect and the spin Hall effect originating from current induced spin–orbit coupling was investigated in the as-deposited and annealed Pt/Co/MgO stacks with perpendicular magnetic anisotropy. The above two effects were analyzed based on Hall measurements under external magnetic fields longitudinal and vertical to dc current, respectively. The coercive field as a function of dc current in vertical mode with only the Rashba effect involved decreases due to thermal annealing. Meanwhile, spin orbit torques calculated from Hall resistance with only the spin Hall effect involved in the longitudinal mode decrease in the annealed sample. The experimental results prove that the bottom Pt/Co interface rather than the Co/MgO top one plays a more critical role in both Rashba effect and spin Hall effect.

  17. Anisotropy, magnetostriction and local chemical order in amorphous TbxFe1-x (0.1

    International Nuclear Information System (INIS)

    Hernando, A.; Prados, C.; Prieto, C.

    1996-01-01

    Local chemical order in amorphous TbFe thin films has been investigated in a variety of compositions, using EXAFS, magnetostriction and anisotropy measurements. Data reported here are consistent with a density of Fe-Tb pairs in the film plane larger than in the perpendicular direction. (orig.)

  18. The anisotropy of Hf diffusion in α-Zr

    International Nuclear Information System (INIS)

    Hood, G.M.; Zou, H.; Roy, J.A.; Schultz, R.J.; Matsuura, N.; Jackson, J.A.

    1995-07-01

    Hf diffusion coefficients (D) have been measured in the temperature interval 870-1100 K, in directions parallel (D pa ) and perpendicular (D pe ) to the c-axis of double-faced, single crystal specimens of both high-purity (HP) and nominally pure (NP) α-Zr single crystals. The diffusion profiles were measured by secondary ion mass spectrometry. Hf diffusion in HP α-Zr is characterised by an activation energy of about 3.0 eV and a pre-exponential factor of about 10 -5 m 2 /s. The anisotropy ratio, D pa /D pe is ∼ 1.0 for the NP specimens. A dependence of D on diffusion time/depth is indicated for some NP experiments on NP Zr. (author). 7 refs., 2 tabs., 3 figs

  19. Fabrication and morphology of uniaxially aligned perylenediimide nanowires

    Science.gov (United States)

    Machida, Shinjiro; Tanikatsu, Makoto; Itaya, Akira; Ikeda, Noriaki

    2017-06-01

    Uniaxial alignment of crystalline nanowires consisting of N,N‧-dioctyl-3,4,9,10-perylenedicarboximide (PTCDI-C8) was achieved on poly(tetrafluoroethylene) (PTFE) layers prepared by friction transfer method on a glass substrate. The nanowires were formed by spin-coating a trifluoroacetic acid (TFA) solution of PTCDI-C8 on the PTFE layers and were further grown under TFA vapor atmosphere. The morphology of the PTCDI-C8 nanowires were characterized using atomic force microscope (AFM) and fluorescence optical microscope with changing the dye concentration in the spin coating solution, annealing time in the TFA vapor, and substrate materials. The nanowires prepared on the PTFE layer on a silica-coated silicon or a mica substrate did not grow so well as those on the glass substrate. This result suggests that the surface roughness would affect the PTFE layer and the growth of the PTCDI nanowires.

  20. Mechanical response of human female breast skin under uniaxial stretching.

    Science.gov (United States)

    Kumaraswamy, N; Khatam, Hamed; Reece, Gregory P; Fingeret, Michelle C; Markey, Mia K; Ravi-Chandar, Krishnaswamy

    2017-10-01

    Skin is a complex material covering the entire surface of the human body. Studying the mechanical properties of skin to calibrate a constitutive model is of great importance to many applications such as plastic or cosmetic surgery and treatment of skin-based diseases like decubitus ulcers. The main objective of the present study was to identify and calibrate an appropriate material constitutive model for skin and establish certain universal properties that are independent of patient-specific variability. We performed uniaxial tests performed on breast skin specimens freshly harvested during mastectomy. Two different constitutive models - one phenomenological and another microstructurally inspired - were used to interpret the mechanical responses observed in the experiments. Remarkably, we found that the model parameters that characterize dependence on previous maximum stretch (or preconditioning) exhibited specimen-independent universal behavior. Copyright © 2017 Elsevier Ltd. All rights reserved.

  1. Surface Wave Velocity-Stress Relationship in Uniaxially Loaded Concrete

    DEFF Research Database (Denmark)

    Shokouhi, Parisa; Zoëga, Andreas; Wiggenhauser, Herbert

    2012-01-01

    The sonic surface wave (or Rayleigh wave) velocity measured on prismatic concrete specimens under uniaxial compression was found to be highly stress-dependent. At low stress levels, the acoustoelastic effect and the closure of existing microcracks results in a gradual increase in surface wave...... velocities. At higher stress levels, concrete suffers irrecoverable damage: the existing microcracks widen and coalesce and new microcracks form. This progressive damage process leads first to the flattening and eventually the drop in the velocity-stress curves. Measurements on specimens undergoing several...... loading cycles revealed that the velocities show a stress-memory effect in good agreement with the Kaiser effect. Comparing the velocities measured during loading and unloading, the effects of stress and damage on the measured velocities could be differentiated. Moreover, the stress dependency of surface...

  2. Uniaxially aligned ceramic nanofibers obtained by chemical mechanical processing

    Energy Technology Data Exchange (ETDEWEB)

    Tararam, R. [Univ Estadual Paulista – UNESP – Instituto de Química, Rua Prof. Francisco Degni n° 55, CEP 14800-900 Araraquara, SP (Brazil); Foschini, C.R. [Univ Estadual Paulista – UNESP – Faculdade de Engenharia de Bauru, Dept. de Eng. Mecanica, Av. Eng. Luiz Edmundo C. Coube 14-01, CEP 17033-360 Bauru, SP (Brazil); Destro, F.B. [Univ Estadual Paulista – UNESP – Faculdade de Engenharia de Guaratinguetá, Guaratinguetá 12516-410, SP (Brazil); Simões, A.Z., E-mail: alezipo@yahoo.com [Univ Estadual Paulista – UNESP – Faculdade de Engenharia de Guaratinguetá, Guaratinguetá 12516-410, SP (Brazil); Longo, E.; Varela, J.A. [Univ Estadual Paulista – UNESP – Instituto de Química, Rua Prof. Francisco Degni n° 55, CEP 14800-900 Araraquara, SP (Brazil)

    2014-08-01

    For this study, we investigated a simple method to generate well aligned nanofibers over large areas using an organic polymer stretched over the substrate surface With this method, ZnO and CuO 3D parallel nanowire arrays were successfully prepared by calcinations of the polymer fibers. X-ray diffraction (XRD) analysis revealed that the copper oxide has a monoclinic structure while the zinc oxide has a hexagonal structure. Scanning electron microscopy (SEM) analysis showed ceramic nanofibers with an average diameter of 120 nm which were composed of small nanoparticles which are 10 nm in diameter. The ability to obtain uniaxially aligned nanofibers reveals a range of interesting properties with potential applications for sensors, catalysts and energy technologies.

  3. Mechanical properties of graphene nanoribbons under uniaxial tensile strain

    Science.gov (United States)

    Yoneyama, Kazufumi; Yamanaka, Ayaka; Okada, Susumu

    2018-03-01

    Based on the density functional theory with the generalized gradient approximation, we investigated the mechanical properties of graphene nanoribbons in terms of their edge shape under a uniaxial tensile strain. The nanoribbons with armchair and zigzag edges retain their structure under a large tensile strain, while the nanoribbons with chiral edges are fragile against the tensile strain compared with those with armchair and zigzag edges. The fracture started at the cove region, which corresponds to the border between the zigzag and armchair edges for the nanoribbons with chiral edges. For the nanoribbons with armchair edges, the fracture started at one of the cove regions at the edges. In contrast, the fracture started at the inner region of the nanoribbons with zigzag edges. The bond elongation under the tensile strain depends on the mutual arrangement of covalent bonds with respect to the strain direction.

  4. Dynamic hysteresis of a uniaxial superparamagnet: Semi-adiabatic approximation

    International Nuclear Information System (INIS)

    Poperechny, I.S.; Raikher, Yu.L.; Stepanov, V.I.

    2014-01-01

    The semi-adiabatic theory of magnetic response of a uniaxial single-domain ferromagnetic particle is presented. The approach is developed in the context of the kinetic theory and allows for any orientation of the external field. Within this approximation, the dynamic magnetic hysteresis loops in an ac field are calculated. It is demonstrated that they very closely resemble those obtained by the full kinetic theory. The behavior of the effective coercive force is analyzed in detail, and for it a simple formula is proposed. This relation accounts not only for the temperature behavior of the coercive force, as the previous ones do, but also yields the dependence on the frequency and amplitude of the applied field

  5. Uniaxial Compressive Strengths of Rocks Drilled at Gale Crater, Mars

    Science.gov (United States)

    Peters, G. H.; Carey, E. M.; Anderson, R. C.; Abbey, W. J.; Kinnett, R.; Watkins, J. A.; Schemel, M.; Lashore, M. O.; Chasek, M. D.; Green, W.; Beegle, L. W.; Vasavada, A. R.

    2018-01-01

    Measuring the physical properties of geological materials is important for understanding geologic history. Yet there has never been an instrument with the purpose of measuring mechanical properties of rocks sent to another planet. The Mars Science Laboratory (MSL) rover employs the Powder Acquisition Drill System (PADS), which provides direct mechanical interaction with Martian outcrops. While the objective of the drill system is not to make scientific measurements, the drill's performance is directly influenced by the mechanical properties of the rocks it drills into. We have developed a methodology that uses the drill to indicate the uniaxial compressive strengths of rocks through comparison with performance of an identically assembled drill system in terrestrial samples of comparable sedimentary class. During this investigation, we utilize engineering data collected on Mars to calculate the percussive energy needed to maintain a prescribed rate of penetration and correlate that to rock strength.

  6. Nonparaxial propagation of Lorentz-Gauss beams in uniaxial crystal orthogonal to the optical axis.

    Science.gov (United States)

    Wang, Xun; Liu, Zhirong; Zhao, Daomu

    2014-04-01

    Analytical expressions for the three components of nonparaxial propagation of a polarized Lorentz-Gauss beam in uniaxial crystal orthogonal to the optical axis are derived and used to investigate its propagation properties in uniaxial crystal. The influences of the initial beam parameters and the parameters of the uniaxial crystal on the evolution of the beam-intensity distribution in the uniaxial crystal are examined in detail. Results show that the statistical properties of a nonparaxial Lorentz-Gauss beam in a uniaxial crystal orthogonal to the optical axis are closely determined by the initial beam's parameters and the parameters of the crystal: the beam waist sizes-w(0), w(0x), and w(0y)-not only affect the size and shape of the beam profile in uniaxial crystal but also determine the nonparaxial effect of a Lorentz-Gauss beam; the beam profile of a Lorentz-Gauss beam in uniaxial crystal is elongated in the x or y direction, which is determined by the ratio of the extraordinary refractive index to the ordinary refractive index; with increasing deviation of the ratio from unity, the extension of the beam profile augments. The results indicate that uniaxial crystal provides an effective and convenient method for modulating the Lorentz-Gauss beams. Our results may be valuable in some fields, such as optical trapping and nonlinear optics, where a light beam with a special profile and polarization is required.

  7. On the identifiability of the Hill-1948 model with one uniaxial tensile test

    Science.gov (United States)

    Bertin, Morgan; Hild, François; Roux, Stéphane

    2017-06-01

    A uniaxial experiment is performed on an ultra-thin specimen made of 17-7 precipitation hardened stainless steel. An anti-wrinkling setup allows for the characterization of the mechanical behavior with Integrated Digital Image Correlation (IDIC). The result shows that a single uniaxial experiment investigated via IDIC possesses enough data (and even more) to characterize a complete anisotropic elastoplastic model.

  8. Fabrication and characterization of nano-particulate PtCo media for ultra-high density perpendicular magnetic recording

    International Nuclear Information System (INIS)

    Newman, Dave M; Wears, M Lesley; Jollie, Michael; Choo, Desmond

    2007-01-01

    The year-on-year growth in areal recording density maintained now for half a century by the hard disk industry has required a corresponding reduction in the size of the magnetic grains comprising the storage media employed. Grain dimensions are now such that the performance of materials which thus far have served the industry well can no longer be maintained as further reduction in their volume risks breaching the superparamagnetic limit with the attendant loss of data integrity. The high magnetocrystalline anisotropy of the Ll 0 phase of PtCo allows particles as small as 4 nm diameter to remain magnetically stable in the elevated temperature environment typical of disk drive systems. A non-interacting dispersion of nanomagnetic particles suspended in an inert non-magnetic host such that each has its anisotropy axis directed perpendicular to the surface of the medium now constitutes the new ideal for a recording medium. Fabrication by a novel combination of conventional sputtering and thermal processing technologies of a medium closely approximating this ideal is demonstrated. An optimized two-stage fabrication process produces a near mono-dispersion of particles with magnetic activation volumes centred about 5 x 10 23 and crystallized in the L1 0 phase with an orientated tetragonal structure. The characteristics of this medium are discussed as a function of composition and crystalline structure. In the absence of a thermally assisted recording head, experiments are conducted on a degraded form of the medium that is shown to support perpendicular recording at linear densities in excess of 240 kfci (D50 point)

  9. Room temperature deposition of perpendicular magnetic anisotropic Co{sub 3}Pt thin films on glass substrate

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Yu-Shen; Dai, Hong-Yu; Hsu, Yi-Wei [Department of Chemical Engineering and Materials Science, Yuan-Ze University, Chung-Li 32003, Taiwan (China); Ou, Sin-Liang, E-mail: slo@mail.dyu.edu.tw [Department of Materials Science and Engineering, Da-Yeh University, Changhua 51591, Taiwan (China); Chen, Shi-Wei [National Synchrotron Radiation Research Center (NSRRC), Hsinchu 300, Taiwan (China); Lu, Hsi-Chuan; Wang, Sea-Fue [Department of Materials and Mineral Resources Engineering, National Taipei University of Technology, Taipei 106, Taiwan (China); Sun, An-Cheng, E-mail: acsun@saturn.yzu.edu.tw [Department of Chemical Engineering and Materials Science, Yuan-Ze University, Chung-Li 32003, Taiwan (China)

    2017-03-01

    Co{sub 3}Pt alloy thin films were deposited on the glass substrate at room temperature (RT) and 300 °C, which showed high perpendicular magnetic anisotropy (PMA) and isotropy magnetic behaviors, respectively. Co{sub 3}Pt HCP (0002) planes grew along the substrate plane for the films deposited at RT. The easy axis [0001] was consequently vertical to the substrate surface and obtained the predominant PMA. Large magnetic domains and sharp boundary also supported high PMA in RT-deposited samples. On the other hand, the PMA was significantly decreased with increasing the deposition temperature from RT to 300 °C. Hard HCP(0002) and soft A1(111) co-existed in the film and the magnetic exchanged coupling between these two phases induced isotropy magnetic behavior. In addition, the various thicknesses (t) of the RT-deposited Co{sub 3}Pt films were deposited with different base pressures prior to sputtering. The Kerr rotation loops showed high PMA and out-of-plane squareness (S{sub ⊥}) of ~0.9 were found in low base pressure chamber. Within high base pressure chamber, Co{sub 3}Pt films just show magnetic isotropy behaviors. This study provides a fabrication method for the preparation of high PMA HCP-type Co{sub 3}Pt films on the glass substrate without any underlayer at RT. The results could be the base for future development of RT-deposited magnetic alloy thin film with high PMA. - Highlights: • Fabricated high perpendicular magnetic anisotropy Co{sub 3}Pt thin film on glass substrate. • Prepared HCP Co{sub 3}Pt thin film at room temperature. • The key to enhance the PMA of the Co{sub 3}Pt films. • Thinner film is good to fabricate PMA Co{sub 3}Pt thin films.

  10. Roles of spin fluctuation and frustration in the superconductivity of β-(BDA-TTP)2X (X=SbF6,AsF6) under uniaxial compression

    Science.gov (United States)

    Ito, Hiroshi; Ishihara, Tetsuo; Tanaka, Hisaaki; Kuroda, Shin-Ichi; Suzuki, Takeo; Onari, Seiichiro; Tanaka, Yukio; Yamada, Jun-Ichi; Kikuchi, Koichi

    2008-11-01

    β -type BDA-TTP [ BDA-TTP=2,5 -bis(1,3-dithian-2-ylidene)-1,3,4,6-tetrathiapentalene] salts possess high transition temperatures TC reaching 7 K among organic superconductors. TC of β-(BDA-TTP)2X (X=SbF6,AsF6) is studied by resistive measurements under uniaxial compression. TC once increases and takes a maximum under compression parallel to the donor stack while it decreases under compression perpendicular to the donor stack. These results are in agreement with the half-filled Hubbard model on the triangular lattice in which the compression controls the spin fluctuation and frustration in the weak pressure region.

  11. The Cosmic Microwave Background Anisotropy

    Science.gov (United States)

    Bennett, C. L.

    1994-12-01

    The properties of the cosmic microwave background radiation provide unique constraints on the history and evolution of the universe. The first detection of anisotropy of the microwave radiation was reported by the COBE Team in 1992, based on the first year of flight data. The latest analyses of the first two years of COBE data are reviewed in this talk, including the amplitude of the microwave anisotropy as a function of angular scale and the statistical nature of the fluctuations. The two-year results are generally consistent with the earlier first year results, but the additional data allow for a better determination of the key cosmological parameters. In this talk the COBE results are compared with other observational anisotropy results and directions for future cosmic microwave anisotropy observations will be discussed. The National Aeronautics and Space Administration/Goddard Space Flight Center (NASA/GSFC) is responsible for the design, development, and operation of the Cosmic Background Explorer (COBE). Scientific guidance is provided by the COBE Science Working Group.

  12. Simulation of Texture Evolution during Uniaxial Deformation of Commercially Pure Titanium

    Science.gov (United States)

    Bishoyi, B.; Debta, M. K.; Yadav, S. K.; Sabat, R. K.; Sahoo, S. K.

    2018-03-01

    The evolution of texture in commercially pure (CP) titanium during uniaxial tension and compression through VPSC (Visco-plastic self-consistent) simulation is reported in the present study. CP-titanium was subjected to both uniaxial tension and compression upto 35% deformation. During uniaxial tension, tensile twin of \\{10\\bar{1}2\\}\\unicode{x003C;}\\bar{1}011\\unicode{x003E;} type and compressive twin of \\{11\\bar{2}2\\}\\unicode{x003C;}11\\bar{2}\\bar{3}\\unicode{x003E;} type were observed in the samples. However, only tensile twin of \\{10\\bar{1}2\\}\\unicode{x003C;}\\bar{1}011\\unicode{x003E;} type and compressive twin of type was observed in the samples during uniaxial compression. Volume fractions of the twins were increased linearly as a function of percentage deformation during uniaxial tension. Whereas, during uniaxial compression the twinning volume fraction was increased up to 20% deformation and then decreased rapidly on further increasing the percentage deformation. During uniaxial tension, the general t-type textures were observed in the samples irrespective of the percentage deformation. The initial non-basal texture was oriented to split basal texture during uniaxial compression of the sample. VPSC formulation was used for simulating the texture development in the material. Different hardening parameters were estimated through correlating the simulated stress-strain curve with the experimental stress-strain data. It was observed that, prismatic slip \\{10\\bar{1}0\\}\\unicode{x003C;}11\\bar{2}0\\unicode{x003E;} operated as the primary deformation mode during uniaxial tension whereas basal slip \\{0001\\}\\unicode{x003C;}11\\bar{2}0\\unicode{x003E;} acquired the leading role during deformation through uniaxial compression. It was also revealed that active deformation modes were fully depending on percentage deformation, loading direction, and orientation of grains.

  13. Anisotropy of acoustic properties in paratellurite

    International Nuclear Information System (INIS)

    Parygin, Vladimir N.

    1996-01-01

    One of the peculiarities of the TeO 2 crystal consists of its strong acoustic anisotropy. This anisotropy demonstrates itself by acoustic energy walk-off and anisotropic distortion of an acoustic beam. Four constants completely characterise the acoustic anisotropy of the medium. In this paper these constants are calculated for various directions of the acoustic beam in crystal. (authors)

  14. Magnetic anisotropies and magnetic switching in Co films

    Science.gov (United States)

    Bland, J. A. C.; Baird, M. J.; Leung, H. T.; Ives, A. J. R.; Mackay, K. D.; Hughes, H. P.

    1992-07-01

    We have used the magneto-optical Kerr effect to investigate the role of the substrate and growth conditions in determining the magnetic switching behaviour of Co films in the thickness range 100-200 Å supported by GaAs(001) and Si(111) substrates. We discuss the anisotropic magnetic hysteresis behaviour observed for Co/GaAs and Co/Si films in terms of coherent rotation of the magnetisation vector during magnetic switching. Equivalent films supported by glass substrates are found to be almost isotropic in-plane. The in-plane coercive and saturation fields are observed to lie in the range 20-80 Oe but perpendicular saturation fields of 25 and 19 kOe are found for the Co/Si and Co/GaAs systems respectively which substantially exceed the demagnetising field in each case. The measured perpendicular anisotropy fields differ strongly from the values for hcp and bcc Co and are attributed to the details of the interface and film structure. We also report strongly frequency dependent magnetic switching behaviour in these Co films.

  15. Effect of Cu buffer layer on magnetic anisotropy of cobalt thin films deposited on MgO(001 substrate

    Directory of Open Access Journals (Sweden)

    Syed Sheraz Ahmad

    2016-11-01

    Full Text Available Cobalt thin films with 5 nm thickness were prepared on single-crystal MgO (001 substrates with different thickness Cu buffer (0 nm, 5 nm, 10 nm, 20 nm. The structure, magnetic properties and transport behaviors were investigated by employing low-energy-electron-diffraction (LEED, magneto-optical Kerr effect (MOKE and anisotropic magnetoresistance (AMR. By comparing the magnetic properties of the sample as-deposited (without Cu buffer layer one with those having the buffer Cu, we found that the magnetic anisotropy was extremely affected by the Cu buffer layer. The magnetic anisotropy of the as-deposited, without buffer layer, sample shows the uniaxial magnetic anisotropy (UMA. We found that the symmetry of the magnetic anisotropy is changed from UMA to four-fold when the thickness of the Cu buffer layer reaches to 20 nm. Meanwhile, the coercivity increased from 49 Oe (without buffer layer to 300 Oe (with 20 nm Cu buffer, in the easy axis direction, as the thickness of the buffer layer increases. Moreover, the magnitudes of various magnetic anisotropy constants were determined from torque curves on the basis of AMR results. These results support the phenomenon shown in the MOKE.

  16. Uniaxial-pressure dependence of the magnetization dynamics in the high-symmetry single-molecule magnet Mn12-MeOH

    Science.gov (United States)

    Atkinson, James H.; Bhaskaran, Lakshmi; Hill, Stephen; Myasoedov, Yuri; Zeldov, Eli; Del Barco, Enrique; Friedman, Jonathan; Fournet, Adeline; Christou, George

    2015-03-01

    The single-molecule magnet [Mn12O12(O2CCH3)16(CH3OH)4]CH3OH (``Mn12-MeOH'') is a high-symmetry sibling of the Mn12-Acetate SMM that offers a prime opportunity to explore the consequences of molecular symmetry. A previous study has shown that applied pressure induced changes in the Mn12-Acetate's anisotropy parameters. Here we present the results of a study in which uniaxial pressure was applied to a crystalline sample of Mn12-MeOH in order to examine how the pressure affects the quantum tunneling of magnetization at low temperature. We find that the pressure induces an increase in the resonant tunneling rate manifested as a change in the height of the tunneling steps in the magnetic hysteresis. These results suggest that pressure is altering symmetry-breaking terms in the molecule's spin Hamiltonian, giving rise to increased tunneling.

  17. Magnetic anisotropy of lecithin membranes. A new anisotropy susceptometer

    OpenAIRE

    Scholz, F.; Boroske, E.; Helfrich, W.

    1984-01-01

    Cylindrical giant vesicles prepared from egg lecithin and 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) are oriented in an external magnetic field and observed by phase contrast microscopy. The anisotropic part of the diamagnetic susceptibility of the lecithin membrane is determined from the distribution of angles between the magnetic field and the long cylinder axis due to thermal fluctuations. The anisotropy of DMPC is found to be larger by a factor of 2 than that of egg lecithin. This...

  18. Magnetic anisotropy and anisotropic ballistic conductance of thin magnetic wires

    International Nuclear Information System (INIS)

    Sabirianov, R.

    2006-01-01

    The magnetocrystalline anisotropy of thin magnetic wires of iron and cobalt is quite different from the bulk phases. The spin moment of monatomic Fe wire may be as high as 3.4 μ B , while the orbital moment as high as 0.5 μ B . The magnetocrystalline anisotropy energy (MAE) was calculated for wires up to 0.6 nm in diameter starting from monatomic wire and adding consecutive shells for thicker wires. I observe that Fe wires exhibit the change sign with the stress applied along the wire. It means that easy axis may change from the direction along the wire to perpendicular to the wire. We find that ballistic conductance of the wire depends on the direction of the applied magnetic field, i.e. shows anisotropic ballistic magnetoresistance. This effect occurs due to the symmetry dependence of the splitting of degenerate bands in the applied field which changes the number of bands crossing the Fermi level. We find that the ballistic conductance changes with applied stress. Even for thicker wires the ballistic conductance changes by factor 2 on moderate tensile stain in our 5x4 model wire. Thus, the ballistic conductance of magnetic wires changes in the applied field due to the magnetostriction. This effect can be observed as large anisotropic BMR in the experiment

  19. Spin structure factors of Heisenberg spin chain in the presence of anisotropy and magnetic field

    International Nuclear Information System (INIS)

    Rezania, H.

    2017-01-01

    We have theoretically studied the spin structure factors of spin chain in the presence of longitudinal field and transverse anisotropy. The possible effects of easy axis magnetization are investigated in terms of anisotropy in the Heisenberg interactions. This anisotropy is considered for exchange coupling constants perpendicular to magnetic field direction. The original spin model hamiltonian is mapped to a bosonic model via a hard core bosonic transformation where an infinite hard core repulsion is imposed to constrain one boson occupation per site. Using Green's function approach, the energy spectrum of quasiparticle excitation has been obtained. The spectrum of the bosonic gas has been implemented in order to obtain two particle propagator which corresponds to spin structure factor of original Heisenberg chain model Hamiltonian. The results show the position of peak in the longitudinal structure factor at fixed value for anisotropy moves to higher frequency with magnetic field. Also the intensity of dynamical structure factor decreases with magnetic field. A small dependence of longitudinal dynamical spin structure factor on the anisotropy is observed for fixed value of magnetic field. Our results show longitudinal static structure factor is found to be monotonically increasing with magnetic field due to increase of spins aligning along magnetic field. Furthermore the dispersion behaviors of static longitudinal and transverse structure factors for different magnetic fields and anisotropy parameters are addressed. - Highlights: • Theoretical calculation of spin structure factors of Heisenberg chain. • The investigation of the effect of anisotropy spin structure factors of Heisenberg chain. • The investigation of the effect of magnetic field on spin structure factors of Heisenberg chain.

  20. Spin structure factors of Heisenberg spin chain in the presence of anisotropy and magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Rezania, H., E-mail: rezania.hamed@gmail.com

    2017-02-01

    We have theoretically studied the spin structure factors of spin chain in the presence of longitudinal field and transverse anisotropy. The possible effects of easy axis magnetization are investigated in terms of anisotropy in the Heisenberg interactions. This anisotropy is considered for exchange coupling constants perpendicular to magnetic field direction. The original spin model hamiltonian is mapped to a bosonic model via a hard core bosonic transformation where an infinite hard core repulsion is imposed to constrain one boson occupation per site. Using Green's function approach, the energy spectrum of quasiparticle excitation has been obtained. The spectrum of the bosonic gas has been implemented in order to obtain two particle propagator which corresponds to spin structure factor of original Heisenberg chain model Hamiltonian. The results show the position of peak in the longitudinal structure factor at fixed value for anisotropy moves to higher frequency with magnetic field. Also the intensity of dynamical structure factor decreases with magnetic field. A small dependence of longitudinal dynamical spin structure factor on the anisotropy is observed for fixed value of magnetic field. Our results show longitudinal static structure factor is found to be monotonically increasing with magnetic field due to increase of spins aligning along magnetic field. Furthermore the dispersion behaviors of static longitudinal and transverse structure factors for different magnetic fields and anisotropy parameters are addressed. - Highlights: • Theoretical calculation of spin structure factors of Heisenberg chain. • The investigation of the effect of anisotropy spin structure factors of Heisenberg chain. • The investigation of the effect of magnetic field on spin structure factors of Heisenberg chain.

  1. Investigation of the use of uniaxial comb-shaped Galfenol patches for a guided wave-based magnetostrictive phased array sensor

    Science.gov (United States)

    Yoo, Byungseok; Pines, Darryll J.

    2018-05-01

    This paper investigates the use of uniaxial comb-shaped Fe-Ga alloy (Galfenol) patches in the development of a Magnetostrictive Phased Array Sensor (MPAS) for the Guided Wave (GW) damage inspection technique. The MPAS consists of six highly-textured Galfenol patches with a preferred orientation and a Hexagonal Magnetic Circuit Device (HMCD). The Galfenol patches individually aligned to distinct azimuthal directions were permanently attached to a thin aluminum plate specimen. The detachable HMCD encloses a biasing magnet and six sensing coils with unique directional sensing preferences, equivalent to the specific orientation of the discrete Galfenol patches. The preliminary experimental tests validated that the GW sensing performance and directional sensitivity of the Galfenol-based sensor were significantly improved by the magnetic shape anisotropy effect on the fabrication of uniaxial comb fingers to a Galfenol disc patch. We employed a series of uniaxial comb-shaped Galfenol patches to form an MPAS with a hexagonal sensor configuration, uniformly arranged within a diameter of 1". The Galfenol MPAS was utilized to identify structural damage simulated by loosening joint bolts used to fasten the plate specimen to a frame structure. We compared the damage detection results of the MPAS with those of a PZT Phased Array Sensor (PPAS) collocated to the back surface of the plate. The directional filtering characteristic of the Galfenol MPAS led to acquiring less complicated GW signals than the PPAS using omnidirectional PZT discs. However, due to the detection limit of the standard hexagonal patterned array, the two array sensors apparently identified only the loosened bolts located along one of the preferred orientations of the array configuration. The use of the fixed number of the Galfenol patches for the MPAS construction constrained the capability of sensing point multiplication of the HMCD by altering its rotational orientation, resulting in such damage detection

  2. Channel modeling, signal processing and coding for perpendicular magnetic recording

    Science.gov (United States)

    Wu, Zheng

    With the increasing areal density in magnetic recording systems, perpendicular recording has replaced longitudinal recording to overcome the superparamagnetic limit. Studies on perpendicular recording channels including aspects of channel modeling, signal processing and coding techniques are presented in this dissertation. To optimize a high density perpendicular magnetic recording system, one needs to know the tradeoffs between various components of the system including the read/write transducers, the magnetic medium, and the read channel. We extend the work by Chaichanavong on the parameter optimization for systems via design curves. Different signal processing and coding techniques are studied. Information-theoretic tools are utilized to determine the acceptable region for the channel parameters when optimal detection and linear coding techniques are used. Our results show that a considerable gain can be achieved by the optimal detection and coding techniques. The read-write process in perpendicular magnetic recording channels includes a number of nonlinear effects. Nonlinear transition shift (NLTS) is one of them. The signal distortion induced by NLTS can be reduced by write precompensation during data recording. We numerically evaluate the effect of NLTS on the read-back signal and examine the effectiveness of several write precompensation schemes in combating NLTS in a channel characterized by both transition jitter noise and additive white Gaussian electronics noise. We also present an analytical method to estimate the bit-error-rate and use it to help determine the optimal write precompensation values in multi-level precompensation schemes. We propose a mean-adjusted pattern-dependent noise predictive (PDNP) detection algorithm for use on the channel with NLTS. We show that this detector can offer significant improvements in bit-error-rate (BER) compared to conventional Viterbi and PDNP detectors. Moreover, the system performance can be further improved by

  3. Voltage fluctuations in granular superconductors in the perpendicular configuration

    International Nuclear Information System (INIS)

    Gerashchenko, O V

    2003-01-01

    The spectral density of voltage fluctuations in granular YBa 2 Cu 3 O 7-δ superconductors in the perpendicular configuration has been studied in the flux flow mode. It has been found that, in this case, the 1/f-voltage noise observed depends weakly on temperature and is associated with motion of a magnetic flux in the superconductor. A comparison of the data obtained with the results of previous measurements in parallel configuration has shown that voltage noise is produced by a single common source, which is presumably associated with self-organization of the critical state in granular superconductors

  4. Superparamagnetic perpendicular magnetic tunnel junctions for true random number generators

    Science.gov (United States)

    Parks, Bradley; Bapna, Mukund; Igbokwe, Julianne; Almasi, Hamid; Wang, Weigang; Majetich, Sara A.

    2018-05-01

    Superparamagnetic perpendicular magnetic tunnel junctions are fabricated and analyzed for use in random number generators. Time-resolved resistance measurements are used as streams of bits in statistical tests for randomness. Voltage control of the thermal stability enables tuning the average speed of random bit generation up to 70 kHz in a 60 nm diameter device. In its most efficient operating mode, the device generates random bits at an energy cost of 600 fJ/bit. A narrow range of magnetic field tunes the probability of a given state from 0 to 1, offering a means of probabilistic computing.

  5. Finite-element modeling and micromagnetic modeling of perpendicular writers

    Science.gov (United States)

    Heinonen, Olle; Bozeman, Steven P.

    2006-04-01

    We compare finite-element modeling (FEM) and fully micromagnetic modeling results of four prototypical writers for perpendicular recording. In general, the agreement between the two models is quite good in the vicinity of saturated or near-saturated magnetic material, such as the pole tip, for quantities such as the magnetic field, the gradient of the magnetic field and the write width. However, in the vicinity of magnetic material far from saturation, e.g., return pole or trailing edge write shield, there can be large qualitative and quantitative differences.

  6. Current perpendicular to plane giant magnetoresistance in laminated nanostructures

    International Nuclear Information System (INIS)

    Vedyayev, A.; Zhukov, I.; Dieny, B.

    2005-01-01

    We theoretically studied spin-dependent electron transport perpendicular-to-plain (CPP) in magnetic laminated multilayered structures by using Kubo formalism. We took into account not only bulk scattering, but the interface resistance due to both specular and diffuse reflection and also spin conserving and spin-flip processes. It was shown that spin-flip scattering at interfaces substantially reduces the value of giant magnetoresistance (GMR). This can explain the experimental observations that the CPP GMR ratio for laminated structures only slightly increases as compared to non-laminated ones even though lamination induces a significant increase in CPP resistance

  7. Temperature anisotropy instabilities in a plasma containing cold and hot species in the magnetosphere

    International Nuclear Information System (INIS)

    Renuka, G.; Viswanathan, K.S.

    1980-01-01

    The nature of convective instability has been investigated for an electromagnetic wave, either right circularly polarised or left circularly polarised, propagating along a magnetic line of force in a plasma whose distribution function exhibits a temperature anisotropy in the hot species, a loss cone structure and a beam of cold electrons or ions travelling along the line of force with velocity V 1 . Detailed numerical calculations have been made using a computer for the growth and decay of the wave for different values of the anisotropy ratio Tsub(perpendicular to)/Tsub(parallel to) delta of the perpendicular and parallel temperatures, the McIlwain parameter L, the loss cone index j, velocity V 1 of the streaming particle and the particle density ratio epsilon. The ranges of the values of epsilon and delta for which the waves becomes unstable have been studied in detail. It is found that wave propagation shows no dependence on the loss cone index but shows very strong dependence on the temperature anisotropy delta. (author)

  8. Numerical modeling of the 22-year variation of the cosmic ray intensity and anisotropy

    International Nuclear Information System (INIS)

    Kadokura, A.; Nishida, A.

    1986-01-01

    We have solved the two-dimensional time-dependent diffusion-convection equation numerically to obtain the distribution and anisotropy of cosmic rays in the heliosphere. We have assumed that the parallel and perpendicular mean free paths are proportional to the particle Larmor radius, and we have treated each proportionality constant (a,b) as a parameter. We have found that the set (a,b) = (4,2) gives the steady state solution compatible with observations on the intensity and the solar diurnal anisotropy of cosmic rays in 0.5- to 10-GeV range as obtained at the earth. This set of (a,b) corresponds to the ratio of the diffusion coefficients D/sub parallel//D/sub perpendicular/ = 10. In our solution the intensity for the (pre-1980) interplanetary magnetic field (IMF) state where the solar magnetic dipole and the angular velocity vector are parallel is higher than for the (post-1980) state where they are antiparallel, while the phase of the diurnal anisotropy is about 15 hours for the parallel state and about 18 hours for the antiparallel state. We have also reproduced the observed small radial gradient for each IMF state. We discuss the nature of the solution in order to understand the effect of the density gradient drift motion on the cosmic ray distribution

  9. Effects of ion temperature anisotropy on the interhemispheric plasma transport during plasmaspheric refilling

    International Nuclear Information System (INIS)

    Singh, N.; Torr, D.G.

    1990-01-01

    Effects of temperature anisotropies on the early stage refilling of the outer plasmasphere are studied by solving an appropriate set of hydrodynamic equations. The anisotropies result from the supersonic outflows from the conjugate ionospheres and from the perpendicular ion heating in the equatorial region. The equatorial ion heating affected by wave-particle interaction is included phenomenologically. Even for the equatorial heating associated with moderate wave levels, the mirror force on the flows severely limits the interhemispheric plasma exchange. The temporal evolution of the flow developing in an empty flux tube is characterized by: (1) supersonic plasma outflows from the conjugate ionospheres, (2) reflections of the flows by the mirror force as they begin to penetrate into the opposite hemispheres, (3) formation of shocks in the reflection region and (4) propagations of the shocks to the ionospheres of the origins of the flows. In the quasi-steady state when flow completely subsides, the density distribution in the flux tube shows distinctive large-scale features, determined by the balance between electric, pressure and anisotropy forces. The latter force becomes significant in a broad equatorial region where T t >> T p and also at relatively high geomagnetic latitudes where T t p ; T t and T p are the perpendicular and parallel ion temperatures, respectively

  10. Uniaxial strain effects on transport properties of a supramolecular organic conductor theta-(DIETS) sub 2 [Au(CN) sub 4

    CERN Document Server

    Tajima, N; Kato, R; Nishio, Y; Kajita, K

    2003-01-01

    Pressure-controlled switching between an insulating state and a superconducting state has been successfully realized on a supramolecular organic conductor theta-(DIETS) sub 2 [Au(CN) sub 4] [DIETS = diiodo(ethylenedithio)diselenadithiafulvalene]. Strong contact between iodine on the donor (DIETS) molecule and nitrogen on the anion [Au(CN) sub 4] genetates characteristic uniaxial strain effects on transport properties. Under the ambient pressure, the present system undergoes a semiconductor-insulator transition at 226 K. The effect of strains parallel to the conduction plane (ab-plane) is very small. Even under uniaxial strains up to 20 kbar along the a- and b-axis directions, the transition is not suppressed. Surprisingly, however, the c-axis strain induces a superconducting state with T sub c of 8.6 K at 10 kbar. Band parameter calculation and the conductivity anisotropy ratio suggest that an increase in the bandwidth W associated with a c-axis strain transforms the system to the metallic and superconducting...

  11. Influence of planar macrodefects on the anisotropy of magnetic-flux penetration in YBa 2Cu 3O 7-δ

    Science.gov (United States)

    Cuche, E.; Indenbom, M. V.; André, M.-O.; Richard, P.; Benoit, W.; Wolf, Th.

    1996-02-01

    The magnetic flux penetration in a high-quality YBa 2Cu 3O 7-δ single crystal with an external field applied perpendicular to the crystalline c axis is directly visualized by means of the magneto-optical technique. The observations show that the field penetrates preferentially along the ab planes. Scanning acoustic microscopy reveals macrodefects along ab planes which strongly affect this anisotropy of the field penetration.

  12. Physics in a general length space-time geometry: Call for experimental revision of the light speed anisotropy

    OpenAIRE

    Exirifard, Qasem

    2013-01-01

    We present a phenomenological model for the nature in the Finsler and Randers space-time geometries. We show that the parity-odd light speed anisotropy perpendicular to the gravitational equipotential surfaces encodes the deviation from the Riemann geometry toward the Randers geometry. We utilize an asymmetrical ring resonator and propose a setup in order to directly measure this deviation. We address the constraints that the current technology will impose on the deviation should the anisotro...

  13. Perpendicular STT_RAM cell in 8 nm technology node using Co1/Ni3(1 1 1)||Gr2||Co1/Ni3(1 1 1) structure as magnetic tunnel junction

    Science.gov (United States)

    Varghani, Ali; Peiravi, Ali; Moradi, Farshad

    2018-04-01

    The perpendicular anisotropy Spin-Transfer Torque Random Access Memory (P-STT-RAM) is considered to be a promising candidate for high-density memories. Many distinct advantages of Perpendicular Magnetic Tunnel Junction (P-MTJ) compared to the conventional in-plane MTJ (I-MTJ) such as lower switching current, circular cell shape that facilitates manufacturability in smaller technology nodes, large thermal stability, smaller cell size, and lower dipole field interaction between adjacent cells make it a promising candidate as a universal memory. However, for small MTJ cell sizes, the perpendicular technology requires new materials with high polarization and low damping factor as well as low resistance area product of a P-MTJ in order to avoid a high write voltage as technology is scaled down. A new graphene-based STT-RAM cell for 8 nm technology node that uses high perpendicular magnetic anisotropy cobalt/nickel (Co/Ni) multilayer as magnetic layers is proposed in this paper. The proposed junction benefits from enough Tunneling Magnetoresistance Ratio (TMR), low resistance area product, low write voltage, and low power consumption that make it suitable for 8 nm technology node.

  14. DRIFT-INDUCED PERPENDICULAR TRANSPORT OF SOLAR ENERGETIC PARTICLES

    International Nuclear Information System (INIS)

    Marsh, M. S.; Dalla, S.; Kelly, J.; Laitinen, T.

    2013-01-01

    Drifts are known to play a role in galactic cosmic ray transport within the heliosphere and are a standard component of cosmic ray propagation models. However, the current paradigm of solar energetic particle (SEP) propagation holds the effects of drifts to be negligible, and they are not accounted for in most current SEP modeling efforts. We present full-orbit test particle simulations of SEP propagation in a Parker spiral interplanetary magnetic field (IMF), which demonstrate that high-energy particle drifts cause significant asymmetric propagation perpendicular to the IMF. Thus in many cases the assumption of field-aligned propagation of SEPs may not be valid. We show that SEP drifts have dependencies on energy, heliographic latitude, and charge-to-mass ratio that are capable of transporting energetic particles perpendicular to the field over significant distances within interplanetary space, e.g., protons of initial energy 100 MeV propagate distances across the field on the order of 1 AU, over timescales typical of a gradual SEP event. Our results demonstrate the need for current models of SEP events to include the effects of particle drift. We show that the drift is considerably stronger for heavy ion SEPs due to their larger mass-to-charge ratio. This paradigm shift has important consequences for the modeling of SEP events and is crucial to the understanding and interpretation of in situ observations

  15. Switching a Perpendicular Ferromagnetic Layer by Competing Spin Currents

    Science.gov (United States)

    Ma, Qinli; Li, Yufan; Gopman, D. B.; Kabanov, Yu. P.; Shull, R. D.; Chien, C. L.

    2018-03-01

    An ultimate goal of spintronics is to control magnetism via electrical means. One promising way is to utilize a current-induced spin-orbit torque (SOT) originating from the strong spin-orbit coupling in heavy metals and their interfaces to switch a single perpendicularly magnetized ferromagnetic layer at room temperature. However, experimental realization of SOT switching to date requires an additional in-plane magnetic field, or other more complex measures, thus severely limiting its prospects. Here we present a novel structure consisting of two heavy metals that delivers competing spin currents of opposite spin indices. Instead of just canceling the pure spin current and the associated SOTs as one expects and corroborated by the widely accepted SOTs, such devices manifest the ability to switch the perpendicular CoFeB magnetization solely with an in-plane current without any magnetic field. Magnetic domain imaging reveals selective asymmetrical domain wall motion under a current. Our discovery not only paves the way for the application of SOT in nonvolatile technologies, but also poses questions on the underlying mechanism of the commonly believed SOT-induced switching phenomenon.

  16. Interaction of Mutually Perpendicular Magnetic Fields in HTSC

    Directory of Open Access Journals (Sweden)

    Vasilyev Aleksandr Fedorovich

    2015-11-01

    Full Text Available In this article a problem of interaction of the crossed magnetic fields in superconductors is considered. Superconducting materials have nonlinear magnetic properties. It allows using a non-linear magnetic susceptibility for measurement of feeble magnetic fields. We place a wire of superconducting material in a constant parallel uniform magnetic field. Then we let through a wire the alternating current leak. Interaction of mutual and perpendicular variation magnetic fields, with adequate accuracy is described by Ginzburg-Landau's equations. Approximate solution of the written equations is received. The component of a magnetic field parallel to a wire contains a variable component. Frequency of a variable component of the magnetic field is equal to the doubled current frequency. Amplitude of the variable component of the magnetic field is proportional to strength of the constant magnetic field. The experimental installation for research of interaction of mutually perpendicular magnetic fields is created. The cylinder from HTSC of ceramics of the YBa2Cu3O7-x was used as a sensor. Dependence of amplitude of the second harmonica of a variation magnetic field on strength of a constant magnetic field is received.

  17. [Cosmic Microwave Background (CMB) Anisotropies

    Science.gov (United States)

    Silk, Joseph

    1998-01-01

    One of the main areas of research is the theory of cosmic microwave background (CMB) anisotropies and analysis of CMB data. Using the four year COBE data we were able to improve existing constraints on global shear and vorticity. We found that, in the flat case (which allows for greatest anisotropy), (omega/H)0 less than 10(exp -7), where omega is the vorticity and H is the Hubble constant. This is two orders of magnitude lower than the tightest, previous constraint. We have defined a new set of statistics which quantify the amount of non-Gaussianity in small field cosmic microwave background maps. By looking at the distribution of power around rings in Fourier space, and at the correlations between adjacent rings, one can identify non-Gaussian features which are masked by large scale Gaussian fluctuations. This may be particularly useful for identifying unresolved localized sources and line-like discontinuities. Levin and collaborators devised a method to determine the global geometry of the universe through observations of patterns in the hot and cold spots of the CMB. We have derived properties of the peaks (maxima) of the CMB anisotropies expected in flat and open CDM models. We represent results for angular resolutions ranging from 5 arcmin to 20 arcmin (antenna FWHM), scales that are relevant for the MAP and COBRA/SAMBA space missions and the ground-based interferometer. Results related to galaxy formation and evolution are also discussed.

  18. Experimental study under uniaxial cyclic behavior at room and high temperature of 316L stainless steel

    International Nuclear Information System (INIS)

    Kang Guozheng; Gao Qing; Yang Xianjie; Sun Yafang

    2001-01-01

    An experimental study was carried out of the cyclic properties of 316L stainless steel subjected to uniaxial strain and stress at room and high temperature. The effects of cyclic strain amplitude, temperature and their histories on the cyclic deformation behavior of 316L stainless steel are investigated. And, the influences of stress amplitude, mean stress, temperature and their histories on ratcheting are also analyzed. It is shown that either uniaxial cyclic property under cyclic strain or ratcheting under asymmetric uniaxial cyclic stress depends not only on the current temperature and loading state, but also on the previous temperature and loading history. Some significant results are obtained

  19. Phase transitions in random uniaxial systems with dipolar interactions

    International Nuclear Information System (INIS)

    Schuster, H.G.

    1977-01-01

    The critical behaviour of random uniaxial ferromagnetic (ferroelectric) systems with both short range and long range dipolar interactions is investigated, using the field theoretic renormalization method of Brezin et al. for the free energy above and below transition point Tsub(c). The randomness is due to externally introduced fluctuations in the short range interactions (quenched case) or (and) magneto-elastic coupling to the lattice (annealed case). Strong deviations in the critical behaviour with respect to the pure systems are found. In the quenched case, e.g., the specific heat C and the coefficient f 2 (of M 3 in the equation of state, where M is the magnetization) change from C proportional to abs ln abs t abs abssup(1/3), f 2 proportional to abs ln abs t abs abs sup(1/3), f 2 proportional to abs ln abs t abs abs -1 in the pure system to C = A+- + C+-exp[-4√ 3 106 abs ln abs t abs abs], f 2 proportional to abs ln abs t abs abs sup(-1/2) (where t = (T-Tsub(c)) / Tsub(c) is the reduced temperature and A+-, C+- are constants) in the random situation. (orig.) [de

  20. Phonon dispersion evolution in uniaxially strained aluminum crystal

    Science.gov (United States)

    Parthasarathy, Ranganathan; Misra, Anil; Aryal, Sitaram; Ouyang, Lizhi

    2018-04-01

    The influence of loading upon the phonon dispersion of crystalline materials could be highly nonlinear with certain particular trends that depend upon the loading path. In this paper, we have calculated the influence of [100] uniaxial strain on the phonon dispersion and group velocities in fcc aluminum using second moments of position obtained from molecular dynamics (MD) simulation at 300 K. In contrast to nonlinear monotonic variation of both longitudinal and transverse phonon frequencies along the Δ , Λ and Σ lines of the first Brillouin zone under tension, transverse phonon branches along the Λ line show inflection at specific wavevectors when the compressive strain exceeds 5%. Further, the longitudinal group velocities along the high-symmetry Δ line vary non-monotonically with strain, reaching a minimum at 5% compressive strain. Throughout the strain range studied, the equilibrium positions of atoms displace in an affine manner preserving certain static structural symmetry. We attribute the anomalies in the phonon dispersion to the non-affine evolution of second moments of atomic position, and the associated plateauing of force constants under the applied strain path.

  1. Failure Mechanisms of Brittle Rocks under Uniaxial Compression

    Science.gov (United States)

    Liu, Taoying; Cao, Ping

    2017-09-01

    The behaviour of a rock mass is determined not only by the properties of the rock matrix, but mostly by the presence and properties of discontinuities or fractures within the mass. The compression test on rock-like specimens with two prefabricated transfixion fissures, made by pulling out the embedded metal inserts in the pre-cured period was carried out on the servo control uniaxial loading tester. The influence of the geometry of pre-existing cracks on the cracking processes was analysed with reference to the experimental observation of crack initiation and propagation from pre-existing flaws. Based on the rock fracture mechanics and the stress-strain curves, the evolution failure mechanism of the fissure body was also analyzed on the basis of exploring the law of the compression-shear crack initiation, wing crack growth and rock bridge connection. Meanwhile, damage fracture mechanical models of a compression-shear rock mass are established when the rock bridge axial transfixion failure, tension-shear combined failure, or wing crack shear connection failure occurs on the specimen under axial compression. This research was of significance in studying the failure mechanism of fractured rock mass.

  2. Mechanical behavior of silicon carbide nanoparticles under uniaxial compression

    Energy Technology Data Exchange (ETDEWEB)

    He, Qiuxiang; Fei, Jing; Tang, Chao; Zhong, Jianxin; Meng, Lijun, E-mail: ljmeng@xtu.edu.cn [Xiangtan University, Hunan Key Laboratory for Micro-Nano Energy Materials and Devices, Faculty of School of Physics and Optoelectronics (China)

    2016-03-15

    The mechanical behavior of SiC nanoparticles under uniaxial compression was investigated using an atomic-level compression simulation technique. The results revealed that the mechanical deformation of SiC nanocrystals is highly dependent on compression orientation, particle size, and temperature. A structural transformation from the original zinc-blende to a rock-salt phase is identified for SiC nanoparticles compressed along the [001] direction at low temperature. However, the rock-salt phase is not observed for SiC nanoparticles compressed along the [110] and [111] directions irrespective of size and temperature. The high-pressure-generated rock-salt phase strongly affects the mechanical behavior of the nanoparticles, including their hardness and deformation process. The hardness of [001]-compressed nanoparticles decreases monotonically as their size increases, different from that of [110] and [111]-compressed nanoparticles, which reaches a maximal value at a critical size and then decreases. Additionally, a temperature-dependent mechanical response was observed for all simulated SiC nanoparticles regardless of compression orientation and size. Interestingly, the hardness of SiC nanocrystals with a diameter of 8 nm compressed in [001]-orientation undergoes a steep decrease at 0.1–200 K and then a gradual decline from 250 to 1500 K. This trend can be attributed to different deformation mechanisms related to phase transformation and dislocations. Our results will be useful for practical applications of SiC nanoparticles under high pressure.

  3. Uniaxial creep behavior of V-4Cr-4Ti alloy

    International Nuclear Information System (INIS)

    Natesan, K.; Soppet, W.K.; Purohit, A.

    2002-01-01

    We are undertaking a systematic study at Argonne National Laboratory to evaluate the uniaxial creep behavior of V-Cr-Ti alloys in a vacuum environment as a function of temperature in the range of 650-800 deg. C and at applied stress levels of 75-380 MPa. Creep strain in the specimens is measured by a linear-variable-differential transducer, which is attached between the fixed and movable pull rods of the creep assembly. Strain is measured at sufficiently frequent intervals during testing to define the creep strain/time curve. A linear least-squares analysis function is used to ensure consistent extraction of minimum creep rate, onset of tertiary creep and creep strain at the onset of tertiary creep. Creep test data, obtained at 650, 700, 725 and 800 deg. C, showed power-law creep behavior. Extensive analysis of the tested specimens is conducted to establish hardness profiles, oxygen content and microstructural characteristics. The data are also quantified by the Larson-Miller approach, and correlations are developed to relate time to rupture, onset of tertiary creep, times for 1% and 2% strain, exposure temperature and applied stress

  4. Influence of anisotropy on anomalous scaling of a passive scalar advected by the Navier-Stokes velocity field.

    Science.gov (United States)

    Jurcisinová, E; Jurcisin, M; Remecký, R

    2009-10-01

    The influence of weak uniaxial small-scale anisotropy on the stability of the scaling regime and on the anomalous scaling of the single-time structure functions of a passive scalar advected by the velocity field governed by the stochastic Navier-Stokes equation is investigated by the field theoretic renormalization group and operator-product expansion within one-loop approximation of a perturbation theory. The explicit analytical expressions for coordinates of the corresponding fixed point of the renormalization-group equations as functions of anisotropy parameters are found, the stability of the three-dimensional Kolmogorov-like scaling regime is demonstrated, and the dependence of the borderline dimension d(c) is an element of (2,3] between stable and unstable scaling regimes is found as a function of the anisotropy parameters. The dependence of the turbulent Prandtl number on the anisotropy parameters is also briefly discussed. The influence of weak small-scale anisotropy on the anomalous scaling of the structure functions of a passive scalar field is studied by the operator-product expansion and their explicit dependence on the anisotropy parameters is present. It is shown that the anomalous dimensions of the structure functions, which are the same (universal) for the Kraichnan model, for the model with finite time correlations of the velocity field, and for the model with the advection by the velocity field driven by the stochastic Navier-Stokes equation in the isotropic case, can be distinguished by the assumption of the presence of the small-scale anisotropy in the systems even within one-loop approximation. The corresponding comparison of the anisotropic anomalous dimensions for the present model with that obtained within the Kraichnan rapid-change model is done.

  5. Strain Rate Effect on Tensile Flow Behavior and Anisotropy of a Medium-Manganese TRIP Steel

    Science.gov (United States)

    Alturk, Rakan; Hector, Louis G.; Matthew Enloe, C.; Abu-Farha, Fadi; Brown, Tyson W.

    2018-06-01

    The dependence of the plastic anisotropy on the nominal strain rate for a medium-manganese (10 wt.% Mn) transformation-induced plasticity (TRIP) steel with initial austenite volume fraction of 66% (balance ferrite) has been investigated. The material exhibited yield point elongation, propagative instabilities during hardening, and austenite transformation to α'-martensite either directly or through ɛ-martensite. Uniaxial strain rates within the range of 0.005-500 s-1 along the 0°, 45°, and 90° orientations were selected based upon their relevance to automotive applications. The plastic anisotropy ( r) and normal anisotropy ( r n) indices corresponding to each direction and strain rate were determined using strain fields obtained from stereo digital image correlation systems that enabled both quasistatic and dynamic measurements. The results provide evidence of significant, orientation-dependent strain rate effects on both the flow stress and the evolution of r and r n with strain. This has implications not only for material performance during forming but also for the development of future strain-rate-dependent anisotropic yield criteria. Since tensile data alone for the subject medium-manganese TRIP steel do not satisfactorily determine the microstructural mechanisms responsible for the macroscopic-scale behavior observed on tensile testing, additional tests that must supplement the mechanical test results presented herein are discussed.

  6. NiO/Fe(001): Magnetic anisotropy, exchange bias, and interface structure

    Energy Technology Data Exchange (ETDEWEB)

    Mlynczak, E. [Jerzy Haber Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, Niezapominajek 8, 30-239 Krakow (Poland); Luches, P. [S3, Istituto Nanoscienze-CNR, Via G. Campi 213/a, I-41125 Modena (Italy); Valeri, S. [S3, Istituto Nanoscienze-CNR, Via G. Campi 213/a, I-41125 Modena (Italy); Dipartimento di Scienze Fisiche, Matematiche e Informatiche, Universita di Modena e Reggio Emilia, Via G. Campi 213/a, 41100 Modena (Italy); Korecki, J. [Jerzy Haber Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, Niezapominajek 8, 30-239 Krakow (Poland); Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, al.Mickiewicza 30, 30-059 Krakow (Poland)

    2013-06-21

    The magnetic and structural properties of NiO/Fe epitaxial bilayers grown on MgO(001) were studied using magnetooptic Kerr effect (MOKE) and conversion electron Moessbauer spectroscopy (CEMS). The bilayers were prepared under ultra high vacuum conditions using molecular beam epitaxy with oblique deposition. Two systems were compared: one showing the exchange bias (100ML-NiO/24ML-Fe), ML stands for a monolayer, and another where the exchange bias was not observed (50ML-NiO/50ML-Fe). For both, the magnetic anisotropy was found to be complex, yet dominated by the growth-induced uniaxial anisotropy. The training effect was observed for the 100ML-NiO/24ML-Fe system and quantitatively described using the spin glass model. The composition and magnetic state of the interfacial Fe layers were studied using {sup 57}Fe-CEMS. An iron oxide phase (Fe{sup 3+}{sub 4}Fe{sup 2+}{sub 1}O{sub 7}), as thick as 31 A, was identified at the NiO/Fe interface in the as-deposited samples. The ferrimagnetic nature of the interfacial iron oxide film explains the complex magnetic anisotropy observed in the samples.

  7. Strain Rate Effect on Tensile Flow Behavior and Anisotropy of a Medium-Manganese TRIP Steel

    Science.gov (United States)

    Alturk, Rakan; Hector, Louis G.; Matthew Enloe, C.; Abu-Farha, Fadi; Brown, Tyson W.

    2018-04-01

    The dependence of the plastic anisotropy on the nominal strain rate for a medium-manganese (10 wt.% Mn) transformation-induced plasticity (TRIP) steel with initial austenite volume fraction of 66% (balance ferrite) has been investigated. The material exhibited yield point elongation, propagative instabilities during hardening, and austenite transformation to α'-martensite either directly or through ɛ-martensite. Uniaxial strain rates within the range of 0.005-500 s-1 along the 0°, 45°, and 90° orientations were selected based upon their relevance to automotive applications. The plastic anisotropy (r) and normal anisotropy (r n) indices corresponding to each direction and strain rate were determined using strain fields obtained from stereo digital image correlation systems that enabled both quasistatic and dynamic measurements. The results provide evidence of significant, orientation-dependent strain rate effects on both the flow stress and the evolution of r and r n with strain. This has implications not only for material performance during forming but also for the development of future strain-rate-dependent anisotropic yield criteria. Since tensile data alone for the subject medium-manganese TRIP steel do not satisfactorily determine the microstructural mechanisms responsible for the macroscopic-scale behavior observed on tensile testing, additional tests that must supplement the mechanical test results presented herein are discussed.

  8. Designing electronic anisotropy of three-dimensional carbon allotropes for the all-carbon device

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Li-Chun, E-mail: xulichun@tyut.edu.cn; Song, Xian-Jiang; Yang, Zhi; Li, Xiu-Yan [College of Physics and Optoelectronics, Taiyuan University of Technology, Taiyuan 030024 (China); Wang, Ru-Zhi; Yan, Hui [College of Materials Science and Engineering, Beijing University of Technology, Beijing 100124 (China)

    2015-07-13

    Extending two-dimensional (2D) graphene nanosheets to a three-dimensional (3D) network can enhance the design of all-carbon electronic devices. Based on the great diversity of carbon atomic bonding, we have constructed four superlattice-type carbon allotrope candidates, containing sp{sup 2}-bonding transport channels and sp{sup 3}-bonding insulating layers, using density functional theory. It was demonstrated through systematic simulations that the ultra-thin insulating layer with only three-atom thickness can switch off the tunneling transport and isolate the electronic connection between the adjacent graphene strips, and these alternating perpendicular strips also extend the electron road from 2D to 3D. Designing electronic anisotropy originates from the mutually perpendicular π bonds and the rare partial charge density of the corresponding carriers in insulating layers. Our results indicate the possibility of producing custom-designed 3D all-carbon devices with building blocks of graphene and diamond.

  9. Strength and Anisotropy in Tournemire Shale: Temperature, Pressure and Time Dependences

    Science.gov (United States)

    Bonnelye, A.; Schubnel, A.; Zhi, G.; David, C.; Dick, P.

    2017-12-01

    Time and temperature dependent rock deformation has both scientific and socio-economic implications for natural hazards, the oil and gas industry and nuclear waste disposal. During the past decades, most studies on brittle creep have focused on igneous rocks and porous sedimentary rocks. To our knowledge, only few studies have been carried out on the brittle creep behavior of shale. We conducted a series of creep experiments on shale specimens coming from the French Institute for Nuclear Safety (IRSN) underground research laboratory located in Tournemire, France, under two different temperatures (26°C, 75°C) and confining pressures (10 MPa, 80 MPa), for three orientations (σ1along, perpendicular and 45° to bedding). In these long-term experiments (approximately 10 days), stress and strains were recorded continuously, while ultrasonic acoustic velocities were recorded every 1 15 minutes. The brittle creep failure stress of our Tournemire shale samples was systematically observed 50% higher than its short-term peak strength, with larger final axial strain accumulated. During creep, ultrasonic wave velocities first decreased, and then increased gradually. The magnitude of elastic wave velocity variations showed an important orientation and temperature dependence: velocities measured perpendicular to bedding showed increased variation, variation that was enhanced at higher temperature and higher pressure. The case of complete elastic anisotropy reversal was observed for sample deformed perpendicular to bedding, with amount of axial strain needed to reach anisotropy reversal reduced at higher temperature. SEM observations highlight the competition between crack growth, sealing/healing, and possibly mineral rotation, pressure solution or anisotropic compaction during creep defromation. Our study highlights that the short-term peak strength has little meaning in shale material, which can over-consolidate importantly by `plastic' flow. In addition, we show that elastic

  10. Propagation of high-order circularly polarized Bessel beams and vortex generation in uniaxial crystals

    CSIR Research Space (South Africa)

    Belyi, VN

    2011-05-01

    Full Text Available The authors investigate the generation and transformation of Bessel beams through linear and nonlinear optical crystals. They outline the generation of high-order vortices due to propagation of Bessel beams along the optical axis of uniaxial...

  11. Mechanical properties of uniaxial natural fabric Grewia tilifolia reinforced epoxy based composites: Effects of chemical treatment

    CSIR Research Space (South Africa)

    Jayaramudu, J

    2014-07-01

    Full Text Available The effects of chemical treatment on the mechanical, morphological, and chemical resistance properties of uniaxial natural fabrics, Grewia tilifolia/epoxy composites, were studied. In order to enhance the interfacial bonding between the epoxy matrix...

  12. Spin-reorientation and anisotropy of the magnetization in single crystalline Ho2Co15Si2

    International Nuclear Information System (INIS)

    Tegus, O.

    2000-01-01

    We have studied the magnetic properties of a Ho 2 Co 15 Si 2 single crystal. The easy magnetization direction is parallel to the c-axis in an extended temperature region below the Curie temperature. A spin-reorientation transition takes place at 323 K, leading to an easy magnetization direction perpendicular to the c-axis below this temperature. We have compared the present results with those obtained previously on various R 2 Co 17 single crystals and found that Si substitution not only leads to a sign reversal in the Co sublattice anisotropy but also leads to a substantial anisotropy of the saturation magnetization. Sign and magnitude of the magnetization anisotropy are conserved during the spin-reorientation transition. (orig.)

  13. Properties of a Bound Polaron under a Perpendicular Magnetic Field

    International Nuclear Information System (INIS)

    Liu Jia; Chen Ziyu; Xiao Jinglin; Huo Shufen

    2007-01-01

    We investigate the influence of a perpendicular magnetic field on a bound polaron near the interface of a polar-polar semiconductor with Rashba effect. The external magnetic field strongly changes the ground state binding energy of the polaron and the Rashba spin-orbit (SO) interaction originating from the inversion asymmetry in the heterostructure splits the ground state binding energy of the bound polaron. In this paper, we have shown how the ground state binding energy will be with the change of the external magnetic field, the location of a single impurity, the wave vector of the electron and the electron areal density, taking into account the SO coupling. Due to the presence of the phonons, whose energy gives negative contribution to the polaron's, the spin-splitting states of the bound polaron are more stable, and we find that in the condition of week magnetic field, the Zeeaman effect can be neglected.

  14. Size effect in tension perpendicular to the grain

    DEFF Research Database (Denmark)

    Pedersen, Martin Bo Uhre; Clorius, Christian Odin; Damkilde, Lars

    1999-01-01

    The strength in tension perpendicular to the grain is known to decrease with an increase in the stressed volume. Usually this size effect is explained on a stochastic basis, that is an explanation relying on an increased probability of encountering a strength reducing flaw when the volume...... of the material under stress is increased. This paper presents a small experimental investigation on specimens with well defined structural orientation of the material. The experiments exhibit a larger size effect than expected and furthermore the data and the nature of the failures encountered suggest...... that the size effect can be explained on a deterministic basis. Arguments for such a simple deterministic explanation of size effect is found in finite element modelling using the orthotropic stiffness characteristics in the transverse plane of wood....

  15. Perpendicular eν mass from W decay

    International Nuclear Information System (INIS)

    Barger, V.; Martin, A.G.; Phillips, R.J.N.

    1983-01-01

    Properties of the perpendicular eν mass, defined in terms of transverse momenta p-vectorsub(T) by Msub(T)sup(2)(eν) = 2|p-vectorsub(eT)| |p-vectorsub(νT)| - 2p-vectorsub(eT).p-vectorsub(νT), that make it particularly well suited to W mass and width determinations are examined. An analytic expression for its distribution in W production and subsequent W → eν decay at p-barp colliders, accurate to order approximately equal to 1% is given. A maximum likelihood fit of this formula to the five UA1 events gives Msub(W) = 80.3 +- 3 6 GeV. (author)

  16. Characteristics of thermally assisted magnetic recording in granular perpendicular media

    International Nuclear Information System (INIS)

    Shiino, Hirotaka; Kawana, Mayumi; Miyashita, Eiichi; Hayashi, Naoto; Watanabe, Sadayuki

    2009-01-01

    The effect of thermally assisted magnetic recording using granular perpendicular media with a single-pole-trimmed head has been investigated. A read/write experiment using a spin stand in which the media were heated by laser irradiation demonstrated that the track average amplitude strongly depends on both the position of the write head relative to the center of the laser spot in the down-track direction and on the laser power. Although the signal-to-noise ratio increased with the coercivity of the media, the increment was small; this is thought to be caused by an increase in the switching field distribution of the media with temperature. Our results suggest that the magnetic constant of the media must be optimized with respect to the temperature of writing in order for high-density thermally assisted magnetic recording to be realized

  17. High-Q perpendicular-biased ferrite-tuned cavity

    International Nuclear Information System (INIS)

    Carlini, R.D.; Thiessen, H.A.; Potter, J.M.

    1983-01-01

    Rapid-cycling proton synchrotrons, such as the proposed LAMPF II accelerator, require approximately 10 MV per turn rf with 17% tuning range near 50 MHz. The traditional approach to ferrite-tuned cavities uses a ferrite which is longitudinally biased (rf magnetic field parallel to bias field). This method leads to unacceptably high losses in the ferrite. At Los Alamos, we are developing a cavity with transverse bias (rf magnetic field perpendicular to the bias field) that makes use of the tensor permeability of the ferrite. Modest power tests of a small (10-cm-dia) quarter-wave singly re-entrant cavity tuned by nickel-zinc ferrites and aluminum-doped garnets indicate that the losses in the ferrite can be made negligible compared with the losses due to the surface resistivity of the copper cavity at power levels from 2 to 200 watts

  18. Two-phonon absorption spectra and lattice vibration anisotropy in HfS2

    International Nuclear Information System (INIS)

    Riede, V.; Neumann, H.; Sobotta, H.

    1983-01-01

    The infrared absorption spectra for E-vector perpendicular to c-vector in the two-phonon combination mode range is measured and analysed in order to get additional information about the A/sub 2u/ mode frequencies in HfS 2 . The lattice vibrational properties have been analysed in terms of the polarizable ion model. This model accounts for the long-range Coulomb terms of the charge and the static dipole induced by the structural anisotropy at each anion site

  19. Experimental study on uniaxial cyclic ratcheting behavior of 304 stainless steel at room temperature

    International Nuclear Information System (INIS)

    Yang Xianjie; Gao Qing; Cai Lixun; Liu Yujie

    2004-01-01

    The cyclic tests for 304 stainless steel with solution heat treatment under uni-axial cyclic straining and stressing were carried out systematically. The effects of the cyclic engineering stress amplitude history with constant mean stress, the mean engineering stress history with constant cyclic stress amplitude and the stress amplitude histories with the specific mean stress increment per cycle on the uni-axial ratcheting deformation behavior were investigated. Some significant results are obtained

  20. Anisotropy indices and the effects on the hydric behaviour of natural stone

    Science.gov (United States)

    Fort, Rafael; Alvarez de Buergo, Monica; Varas, Maria Jose; Gomez-Heras, Miguel

    2010-05-01

    anisotropy are those with the highest capillarity coefficient. It can also be observed that for each petrological variety, this capillarity coefficient is higher in the specimens classified as a high level anisotropy class. At the same time, when capillary water is absorbed along the direction perpendicular to the anisotropic planes, the absorption capacity diminishes, no matter the anisotropy level of the stone is. On the contrary, capillary coefficients are higher when measurements are performed in a parallel direction to that of the greatest anisotropy of the stone specimen, where absorption tends to be faster with higher coefficients according to the porosity size and its geometry. These increments are more significant in the stone varieties in which anisotropy is mainly due to fissuring or schistosity planes, or related to stromatolitic planes or oriented minerals accumulation. The arrangement and placing of rocks used as building materials with a significant anisotropy will highly condition the durability and lifetime of a considered element. For that reason, is essential to determine anisotropy indices to obtain the best and most adequate arrangement of stone elements in building works, minimizing water entry and thus, the material decay. Acknowledgements: to both MATERNAS (0505/MAT/0094) and GEOMATERIALES (2009-1629) research programmes, funded by the Regional Government of Madrid; to the CONSOLIDER-INGENIO programme (CSD2007-0058), funded by the Spanish Ministry of Education and Science; and to the Spanish Geological and Mining Institute (IGME) for the specimens preparation and hydric behaviour measurements.

  1. Uniaxial tension test on Rubber at constant true strain rate

    Directory of Open Access Journals (Sweden)

    Sourne H.L.

    2012-08-01

    Full Text Available Elastomers are widely used for damping parts in different industrial contexts because of their remarkable dissipation properties. Indeed, they can undergo severe mechanical loading conditions, i.e., high strain rates and large strains. Nevertheless, the mechanical response of these materials can vary from purely rubber-like to glassy depending on the strain rate undergone. Classically, uniaxial tension tests are made in order to find a relation between the stress and the strain in the material at various strain rates. However, even if the strain rate is searched to be constant, it is the nominal strain rate that is considered. Here we develop a test at constant true strain rate, i.e. the strain rate that is experienced by the material. In order to do such a test, the displacement imposed by the machine is an exponential function of time. This test has been performed with a high speed hydraulic machine for strain rates between 0.01/s and 100/s. A specific specimen has been designed, yielding a uniform strain field (and so a uniform stress field. Furthermore, an instrumented aluminum bar has been used to take into account dynamic effects in the measurement of the applied force. A high speed camera enables the determination of strain in the sample using point tracking technique. Using this method, the stress-strain curve of a rubber-like material during a loading-unloading cycle has been determined, up to a stretch ratio λ = 2.5. The influence of the true strain rate both on stiffness and on dissipation of the material is then discussed.

  2. Anisotropy of the cosmic background radiation

    International Nuclear Information System (INIS)

    Silk, J.

    1988-01-01

    The characteristics of the cosmic microwave background radiation (CBR) are reviewed, focusing on intrinsic anisotropies caused by primordial matter fluctuations. The basic elements of the CBR are outlined and the contributions to anisotropy at different angular scales are discussed. Possible fluctuation spectra that can generate the observed large-scale structure of the universe through gravitational instability and nonlinear evolution are examined and compared with observational searches for cosmic microwave anisotropies. 21 refs

  3. Azimuthal anisotropy measurements by STAR

    Science.gov (United States)

    Yi, Li

    2014-06-01

    The recent study of centrality and transverse momentum (pT) dependence of inclusive charged hardron elliptic anisotropy (v2) at midrapidity (|η|<1.0) in Au+Au collision at √{sNN}=7.7,11.5,19.6,27, and 39 GeV in STAR Beam Energy Scan program is presented. We show that the observed increase of inclusive v2 is mainly due to the average pT increase with energy. In Au+Au 200 GeV collisions, the triangular anisotropy (v3) measurements highly depend on measurement methods; v3 is strongly dependent on Δη. The difference between two- and four-particle cumulants v2{2} and v2{4} for Au+Au and Cu+Cu collision at √{sNN}=62.4 and 200 GeV is used to explore flow fluctuations. Furthermore, by exploiting the symmetry of average flow in pseudorapidity η about midrapidity, the Δη-dependent and independent components are separated using v2{2} and v2{4}.

  4. Azimuthal anisotropy measurements by STAR

    Energy Technology Data Exchange (ETDEWEB)

    Yi, Li

    2014-06-15

    The recent study of centrality and transverse momentum (p{sub T}) dependence of inclusive charged hardron elliptic anisotropy (v{sub 2}) at midrapidity (|η|<1.0) in Au+Au collision at √(s{sub NN})=7.7,11.5,19.6,27, and39 GeV in STAR Beam Energy Scan program is presented. We show that the observed increase of inclusive v{sub 2} is mainly due to the average p{sub T} increase with energy. In Au+Au 200 GeV collisions, the triangular anisotropy (v{sub 3}) measurements highly depend on measurement methods; v{sub 3} is strongly dependent on Δη. The difference between two- and four-particle cumulants v{sub 2}{2} and v{sub 2}{4} for Au+Au and Cu+Cu collision at √(s{sub NN})=62.4 and 200 GeV is used to explore flow fluctuations. Furthermore, by exploiting the symmetry of average flow in pseudorapidity η about midrapidity, the Δη-dependent and independent components are separated using v{sub 2}{2} and v{sub 2}{4}.

  5. Azimuthal anisotropy measurements by STAR

    International Nuclear Information System (INIS)

    Yi, Li

    2014-01-01

    The recent study of centrality and transverse momentum (p T ) dependence of inclusive charged hardron elliptic anisotropy (v 2 ) at midrapidity (|η|<1.0) in Au+Au collision at √(s NN )=7.7,11.5,19.6,27, and39 GeV in STAR Beam Energy Scan program is presented. We show that the observed increase of inclusive v 2 is mainly due to the average p T increase with energy. In Au+Au 200 GeV collisions, the triangular anisotropy (v 3 ) measurements highly depend on measurement methods; v 3 is strongly dependent on Δη. The difference between two- and four-particle cumulants v 2 {2} and v 2 {4} for Au+Au and Cu+Cu collision at √(s NN )=62.4 and 200 GeV is used to explore flow fluctuations. Furthermore, by exploiting the symmetry of average flow in pseudorapidity η about midrapidity, the Δη-dependent and independent components are separated using v 2 {2} and v 2 {4}

  6. Exploring the Tectonic Evolution of the Seafloor using Roughness, Covariance, and Anisotropy in Bathymetry and Marine Gravity

    Science.gov (United States)

    Kalnins, L. M.; Simons, F.

    2017-12-01

    Between the vastness of the oceans and the technological challenges water poses, data scarcity is frequently a limiting factor in studying the tectonic and morphological evolution of the seafloor. It is therefore essential to extract maximum information from the available gravity and bathymetry data, whilst also retaining realistic estimates of uncertainties. Here, we use a frequency-domain maximum-likelihood procedure to map the roughness structure and the nature of the topographic covariance of the seafloor. Rather than requiring us to assume the covariance is Gaussian or exponential, the flexibility of the Matérn form's parameterisation (variance, range, and differentiability) lets us solve for the shape of the covariance and map out its changes without a priori assumptions.We also examine the relationship between gravity and bathymetry through their coherence and admittance, particularly the anisotropy in the relationship. We extend the robust analysis developed to map anisotropy in lithospheric strength in the continents (Kalnins et al., 2015) to the oceanic domain. This method lets us separate out measurements of anisotropy likely to be linked to anisotropy in the long-term mechanical strength of the lithosphere itself; those aligned with anisotropies in the input gravity and bathymetry data; and those that are mathematically significant, but unexplained. Ultimately, we aim to use the statistical analyses to infer geophysical parameters of interest, such as oceanic spreading rate, level of volcanic activity, and potential for energy dissipation in ocean circulation. Our first results show a general alignment of strong directions ridge-parallel and weak directions ridge-perpendicular, suggesting widespread mechanical anisotropy derived from the lithosphere's highly anisotropic formation at mid-ocean ridges. However, this pattern changes markedly near sites of significant intraplate volcanism, where little to no robust anisotropy in strength is recovered. This

  7. Thermoelectric anisotropy in the iron-based superconductor Ba (Fe1-xCox) 2As2

    Science.gov (United States)

    Matusiak, Marcin; Rogacki, Krzysztof; Wolf, Thomas

    2018-06-01

    We report on the in-plane anisotropy of the Seebeck and Nernst coefficients as well as of the electrical resistivity determined for a series of strain-detwinned single crystals of Ba (Fe1-xC ox) 2A s2 . Two underdoped samples (x =0.024 , 0.045) exhibiting a transition from the tetragonal paramagnetic phase to the orthorhombic spin density wave (SDW) phase (at Ttr=100 and 60 K, respectively) show an onset of Nernst anisotropy at temperatures above 200 K, which is significantly higher than Ttr. In the optimally doped sample (x =0.06 ) the transport properties also appear to be in-plane anisotropic below T ≈120 K, despite the fact that this particular composition does not show any evidence of long-range magnetic order. However, the anisotropy observed in the optimally doped crystal is rather small, and for the Seebeck and Nernst coefficients the difference between values measured along and across the uniaxial strain has an opposite sign to those observed for underdoped crystals with x =0.024 and 0.045. For these two samples, the insensitivity of the Nernst anisotropy to the SDW transition suggests that the origin of nematicity might be something other than magnetic.

  8. Determination of the saturation magnetization, anisotropy field, mean field interaction, and switching field distribution for nanocrystalline hard magnets

    International Nuclear Information System (INIS)

    McCallum, R. William

    2005-01-01

    For a uniaxial nanocrystalline magnetic material, the determination of the saturation magnetization, M s , requires measurements of the magnetization at fields which exceed the anisotropy field. For a typical RE-Tm compound, where RE=rare earth and Tm=transition metal, this may require fields above 7 T if the approach to saturation law is used. However for an isotropic material composed of a random distribution of non-interacting uniaxial grains, both M s and the anisotropy filed, H a , may be determined by fitting the Stoner-Wohlfarth (SW) model (Philos. Trans. Roy. Soc. 240 (1948) 599) to the reversible part of the demagnetization curve in the first quadrant. Furthermore, using the mean field interaction model of Callen, Liu and Cullen [2], a quantitative measure of the interaction strength for interacting particles may be determined. In conjunction with an analytical fit to the first quadrant demagnetization curve of the SW model, this allows M s , H a and the mean field interaction constant of a nanocrystalline magnet to be determined from measurements below 5 T. Furthermore, comparison of the model solution for the reversible magnetization with experimental data in the 2nd and 3rd quadrants allows the accurate determination of the switching field distribution. In many cases the hysteresis loop may be accurately described by a normal distribution of switching fields

  9. Pore Fluid Effects on Shear Modulus for Sandstones with Soft Anisotropy

    International Nuclear Information System (INIS)

    Berryman, J G

    2004-01-01

    A general analysis of poroelasticity for vertical transverse isotropy (VTI) shows that four eigenvectors are pure shear modes with no coupling to the pore-fluidmechanics. The remaining two eigenvectors are linear combinations of pure compression and uniaxial shear, both of which are coupled to the fluid mechanics. After reducing the problem to a 2x2 system, the analysis shows in a relatively elementary fashion how a poroelastic system with isotropic solid elastic frame, but with anisotropy introduced through the poroelastic coefficients, interacts with the mechanics of the pore fluid and produces shear dependence on fluid properties in the overall mechanical system. The analysis shows, for example, that this effect is always present (though sometimes small in magnitude) in the systems studied, and can be quite large (up to a definite maximum increase of 20 per cent) in some rocks--including Spirit River sandstone and Schuler-Cotton Valley sandstone

  10. Dynamic Uniaxial Compression of HSLA-65 Steel at Elevated Temperatures

    Science.gov (United States)

    Dike, Shweta; Wang, Tianxue; Zuanetti, Bryan; Prakash, Vikas

    2017-12-01

    In the present study, the dynamic response of a high-strength, low alloy Grade 65 (HSLA-65) steel, used by the United States Navy for ship hull construction, is investigated under dynamic uniaxial compression at temperatures ranging from room temperature to 1000 °C using a novel elevated temperature split-Hopkinson pressure bar. These experiments are designed to probe the dynamic response of HSLA-65 steel in its single α-ferrite phase, mixed α + γ-austenite phase, and the single γ-austenite phase, as a function of temperature. The investigation is conducted at two different average strain rates—1450 and 2100/s. The experimental results indicate that at test temperatures in the range from room temperature to lower than 600 °C, i.e. prior to the development of the mixed α + γ phase, a net softening in flow strength is observed at all levels of plastic strain with increase in test temperatures. As the test temperatures are increased, the rate of this strain softening with temperature is observed to decrease, and at 600 °C the trend reverses itself resulting in an increase in flow stress at all strains tested. This increase in flow stress is understood be due to dynamic strain aging, where solute atoms play a distinctive role in hindering dislocation motion. At 800 °C, a (sharp) drop in the flow stress, equivalent to one-half of its value at room temperature, is observed. As the test temperature are increased to 900 and 1000 °C, further drop in flow stress are observed at all plastic strain levels. In addition, strain hardening in flow stress is observed at all test temperatures up to 600 °C; beyond 800 °C the rate of strain hardening is observed to decrease, with strain softening becoming dominant at temperatures of 900 °C and higher. Moreover, comparing the high strain rate stress versus strain data gathered on HSLA 65 in the current investigation with those available in the literature at quasi-static strain rates, strain-rate hardening can be

  11. Electric field scales at quasi-perpendicular shocks

    Directory of Open Access Journals (Sweden)

    S. N. Walker

    2004-07-01

    Full Text Available This paper investigates the short scale structures that are observed in the electric field during crossings of the quasi-perpendicular bow shock using data from the Cluster satellites. These structures exhibit large amplitudes, as high as 70 m Vm-1 and so make a significant contribution to the overall change in potential at the shock front. It is shown that the scale size of these short-lived electric field structures is of the order of a few cpe. The relationships between the scale size and the upstream Mach number and θBn are studied. It is found that the scale size of these structures decreases with increasing plasma β and as θBn→90°. The amplitude of the spikes remains fairly constant with increasing Ma and appears to increase as θBn→90°.

  12. Two-Channel Metal Detector Using Two Perpendicular Antennas

    Directory of Open Access Journals (Sweden)

    Kyoo Nam Choi

    2014-01-01

    Full Text Available Two-channel metal detector, having two sets of perpendicularly oriented sensor antennas, is proposed to expand detectable size, ranging from mm through cm scale, of metal sensor, while conventional metal sensor is dedicated for detection only in mm or cm scale. The characteristics of the two metal detection sensor channels were investigated, respectively, and the interference effect, while in simultaneous operation, between two sensor channels was discussed. Metal detection channel, having sensitivity in mm scale, showed detectable sensitivity to moving ferrous sphere, with diameter down to 0.7 mm, at 50 kHz exciting frequency and enhanced sensitivity distribution. And metal detection channel having sensitivity in cm scale showed more uniform sensitivity distribution with the flexibility for future modular construction. The effect of interference, while in simultaneous operation of two sensors, resulted in reduced output response, but still within usable detection range. Thus it was feasible to operate two sensors, having different sensitivity range, simultaneously and to extend detection range from mm to cm scale, within practically acceptable interference.

  13. Symmetry breaking of adjacent tracks in perpendicular recording system

    International Nuclear Information System (INIS)

    Xie Huang; Wei Dan

    2007-01-01

    The track density increase in a perpendicular magnetic recording system is limited by the adjacent-track interference (ATI). In this work, a composite micromagnetic simulation model of the read/write process is developed to analyse ATI by the symmetry of signal and noise in two adjacent W = 60 nm tracks with the track pitch of the order of 100 nm. Based on the two-dimensional medium noise distribution of dibit recording, it is found that the noise in the first and later recorded tracks start to be asymmetric when the track pitch is lower than 2 W; if the read width is limited within 2/3 of the write width, the asymmetry of noise appears when the track pitch is less than 1.5 W. At higher recording densities, the signal-to-noise ratio degradation is mainly due to the noise caused by the interference from the signal of the adjacent track. Side writing can be effectively eliminated by the use of a guard band whose width is at least half the track width

  14. Quasi-perpendicular/quasi-parallel divisions of Earth's bow shock

    International Nuclear Information System (INIS)

    Greenstadt, E.W.

    1991-01-01

    Computer-drawn diagrams of the boundaries between quasi-perpendicular and quasi-parallel areas of Earth's bow shock are displayed for a few selected cone angles of static interplanetary magnetic field (IMF). The effect on the boundary of variable IMF in the foreshock is also discussed and shown for one nominal case. The boundaries demand caution in applying them to the realistic, dynamic conditions of the solar wind and in interpreting the effects of small cone angles on the distributions of structures at the shock. However, the calculated, first-order boundaries are helpful in defining areas of the shock where contributions from active structures inherent in quasi-parallel geometry may be distinguishable from those derived secondarily from upstream reflected ion dynamics. The boundaries are also compatible with known behavior of daytime ULF geomagnetic waves and pulsations according to models postulating that cone angle-controlled, time-dependent ULF activity around the subsolar point of the bow shock provides the source of geomagnetic excitation

  15. Higher-order anisotropies in the blast-wave model: Disentangling flow and density field anisotropies

    Energy Technology Data Exchange (ETDEWEB)

    Cimerman, Jakub [Czech Technical University in Prague, FNSPE, Prague (Czech Republic); Comenius University, FMPI, Bratislava (Slovakia); Tomasik, Boris [Czech Technical University in Prague, FNSPE, Prague (Czech Republic); Univerzita Mateja Bela, FPV, Banska Bystrica (Slovakia); Csanad, Mate; Loekoes, Sandor [Eoetvoes Lorand University, Budapest (Hungary)

    2017-08-15

    We formulate a generalisation of the blast-wave model which is suitable for the description of higher-order azimuthal anisotropies of the hadron production. The model includes anisotropy in the density profile as well as an anisotropy in the transverse expansion velocity field. We then study how these two kinds of anisotropies influence the single-particle distributions and the correlation radii of two-particle correlation functions. Particularly we focus on the third-order anisotropy and consideration is given averaging over different orientations of the event plane. (orig.)

  16. Processing, Structural Characterization and Comparative Studies on Uniaxial Tensile Properties of a New Type of Porous Twisted Wire Material

    Directory of Open Access Journals (Sweden)

    Fei Wu

    2015-08-01

    Full Text Available A self-developed rotary multi-cutter device cuts stainless steel wire ropes into segments to fabricate twisted wires. Stainless steel porous twisted wire materials (PTWMs with a spatial composite intertexture structure are produced by the compaction and subsequent vacuum solid-phase sintering of twisted wires. The stainless steel PTWMs show two types of typical uniaxial tensile failure modes, i.e., a 45° angle fracture mode and an auxetic failure mode (the PTWMs expand along the direction perpendicular to the tension. The effects of the sintering parameters, porosities, wire diameters, and sampling direction on the tensile properties of the PTWMs are carefully investigated. By increasing the sintering temperature from 1130 °C to 1330 °C, the tensile strength of the PTWMs with 70% target porosity increased from 7.7 MPa to 28.6 MPa and the total failure goes down to 50%. When increasing the sintering time from 90 min to 150 min, the tensile strength increases from 12.4 MPa to 19.1 MPa and the total failure elongation drops to 78.6%. The tensile strength of the PTWMs increases from 28.9 MPa to 112.7 MPa with decreasing porosity from 69.5% to 46.0%, and the total failure elongation also increases from 14.8% to 40.7%. The tensile strength and the failure strain of the PTWMs with fine wires are higher than those of the PTWMs with coarse wires under the same porosity. Sampling direction has a small influence on the tensile properties of the PTWMs.

  17. Determination of the components of three dimensional vector and tensor anisotropy of cosmic radiation with application to the results of the Musala experiment

    International Nuclear Information System (INIS)

    Somogyi, A.J.

    1976-09-01

    The paper proves that it is possible to interpret the experimental results of the Musala experiment as being consequences of a vector anisotropy with maximum in the direction of the galactic centre and a tensor anisotropy with principal axes in the physically plausible directions of the galactic arm, the normal direction of the galactic plane and the direction perpendicular them, respectively. It is underlined that the interpretation is not the only possible one and, in addition to this, statistical errors are rather large. The results favour the galactic origin of the particles concerned (E=6x10 13 eV). (Sz.N.Z.)

  18. Uniaxial Pressure Effect on the SdH Oscillations in Heavy-Fermion Semimetal CeRu4Sb12

    International Nuclear Information System (INIS)

    Saha, S. R.; Kobayashi, M.; Sugawara, H.; Namiki, T.; Abe, K.; Aoki, Y.; Sato, H.

    2003-01-01

    We report the first successful Shubnikov-de Haas (SdH) experiment under uniaxial pressure in the anomalous heavy-fermion semimetal CeRu 4 Sb 12 . The nature of the quantum oscillations in the magnetoresistance is found to be significantly sensitive to uniaxial pressure. The results reveal that the nearly spherical Fermi surface elongates along the direction of the uniaxial pressure. (author)

  19. Mechanical and electronic properties of monolayer and bilayer phosphorene under uniaxial and isotropic strains.

    Science.gov (United States)

    Hu, Ting; Han, Yang; Dong, Jinming

    2014-11-14

    The mechanical and electronic properties of both the monolayer and bilayer phosphorenes under either isotropic or uniaxial strain have been systematically investigated using first-principles calculations. It is interesting to find that: 1) Under a large enough isotropic tensile strain, the monolayer phosphorene would lose its pucker structure and transform into a flat hexagonal plane, while two inner sublayers of the bilayer phosphorene could be bonded due to its interlayer distance contraction. 2) Under the uniaxial tensile strain along a zigzag direction, the pucker distance of each layer in the bilayer phosphorene can exhibit a specific negative Poisson's ratio. 3) The electronic properties of both the monolayer and bilayer phosphorenes are sensitive to the magnitude and direction of the applied strains. Their band gaps decrease more rapidly under isotropic compressive strain than under uniaxial strain. Also, their direct-indirect band gap transitions happen at the larger isotropic tensile strains compared with that under uniaxial strain. 4) Under the isotropic compressive strain, the bilayer phosphorene exhibits a transition from a direct-gap semiconductor to a metal. In contrast, the monolayer phosphorene initially has the direct-indirect transition and then transitions to a metal. However, under isotropic tensile strain, both the bilayer and monolayer phosphorene show the direct-indirect transition and, finally, the transition to a metal. Our numerical results may open new potential applications of phosphorene in nanoelectronics and nanomechanical devices by external isotropic strain or uniaxial strain along different directions.

  20. Interplay between magnetocrystalline anisotropy and exchange bias in epitaxial CoO/Co films

    International Nuclear Information System (INIS)

    Liu, Hao-Liang; Zeng, Yu-Jia; Van Haesendonck, Chris; Brems, Steven; Temst, Kristiaan; Vantomme, André

    2016-01-01

    The interplay between magnetocrystalline anisotropy and exchange bias is investigated in CoO/Co bilayer films, which are grown epitaxially on MgO (0 0 1), by magnetization reversal measurements based on the anisotropic magnetoresistance (AMR) effect. While an asymmetric magnetization reversal survives after training for cooling field (CF) along the hard axis, the magnetization reversal becomes symmetric and is dominated in both branches of the hysteresis loop by domain wall motion before and after training for CF along the easy axis. When performing an in-plane hysteresis loop perpendicular to the CF, the hysteresis loop along the easy axis becomes asymmetric: magnetization rotation dominates in the ascending branch, while there is a larger contribution of domain wall motion in the descending branch. Furthermore, the azimuthal angular dependence of the AMR shows two minima after performing a perpendicular hysteresis loop, instead of only one minimum after training. Relying on the extended Fulcomer and Charap model, these effects can be related to an increased deviation of the average uncompensated antiferromagnetic magnetization from the CF direction. This model provides a consistent interpretation of training and asymmetry of the magnetization reversal for epitaxial films with pronounced magnetocrystalline anisotropy as well as for the previously investigated polycrystalline films. (paper)

  1. Dynamic Behavior of Spicules Inferred from Perpendicular Velocity Components

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Rahul; Verth, Gary; Erdélyi, Robertus [Solar Physics and Space Plasma Research Centre, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH (United Kingdom)

    2017-05-10

    Understanding the dynamic behavior of spicules, e.g., in terms of magnetohydrodynamic (MHD) wave mode(s), is key to unveiling their role in energy and mass transfer from the photosphere to corona. The transverse, torsional, and field-aligned motions of spicules have previously been observed in imaging spectroscopy and analyzed separately for embedded wave-mode identification. Similarities in the Doppler signatures of spicular structures for both kink and torsional Alfvén wave modes have led to the misinterpretation of the dominant wave mode in these structures and is a subject of debate. Here, we aim to combine line- of-sight (LOS) and plane-of-sky (POS) velocity components using the high spatial/temporal resolution H α imaging-spectroscopy data from the CRisp Imaging SpectroPolarimeter based at the Swedish Solar Telescope to achieve better insight into the underlying nature of these motions as a whole. The resultant three-dimensional velocity vectors and the other derived quantities (e.g., magnetic pressure perturbations) are used to identify the MHD wave mode(s) responsible for the observed spicule motion. We find a number of independent examples where the bulk transverse motion of the spicule is dominant either in the POS or along the LOS. It is shown that the counterstreaming action of the displaced external plasma due to spicular bulk transverse motion has a similar Doppler profile to that of the m = 0 torsional Alfvén wave when this motion is predominantly perpendicular to the LOS. Furthermore, the inferred magnetic pressure perturbations support the kink wave interpretation of observed spicular bulk transverse motion rather than any purely incompressible MHD wave mode, e.g., the m = 0 torsional Alfvén wave.

  2. Refractive indices of K2ZnCl4 crystals in an incommensurate phase under uniaxial stresses

    International Nuclear Information System (INIS)

    Gaba, V.M.; Kogut, Z.O.; Brezvin, R.S.; Stadnik, V.I.

    2010-01-01

    The influence of uniaxial mechanical stresses directed along the principal crystallophysical axes on refractiveindex temperature dependences in K 2 ZnCl 4 crystals was studied. It is established that the refractive indices ni are quite sensitive to uniaxial stresses. Significant baric shifts of the paraphase-incommensurate-commensurate phase transition points to different temperature regions were observed, which is due to the effect of the uniaxial stress on the K 2 ZnCl 4 crystal structure. It is found that applying uniaxial pressure increases the value of the temperature hysteresis of the commensurate-incommensurate phase transition. (authors)

  3. Evaluation of electrical resistivity anisotropy in geological mapping ...

    African Journals Online (AJOL)

    user

    Key words: Electrical resistivity anisotropy, radial vertical electrical sounding, anisotropy polygons. INTRODUCTION ... electrical resistivity survey in the geological interpretation ... resistivity and other electrical or electromagnetic based.

  4. Seismic and resistivity anisotropy analysis at the Low-Noise Underground Laboratory (LSBB) of Rustrel (France)

    Science.gov (United States)

    Zeyen, H. J.; Bereš, J.; Gaffet, S.; Sénéchal, G.; Rousset, D.; Pessel, M.

    2011-12-01

    Many geological materials exhibit anisotropic behaviour. A limestone massif, especially if cracked with fractures and faults in a predominant orientation is expected to manifest seismic and electric resistivity anisotropy. Seismic velocity within air- or water-filled cracks is smaller than in the rock matrix. Therefore, the velocity parallel to fractures, controlled mainly by the rock matrix, is expected to be faster than perpendicular to the fractures, where waves have to cross fractures and rock matrix. Seismic and resistivity measurements were conducted in three underground galleries of the Low-Noise Underground Gallery (LSBB) in southern France forming a horse-shoe setting. The galleries are located inside a karstic limestone massif. Around 22500 first arrival travel-times were picked and different types of pole-pole and dipole-dipole resistivity measurement were carried out in parallel. Resistivities and velocities vary strongly with direction of observation. The direction of fast velocities is at right angle with the one of slow velocities, a typical sign for anisotropy. Observation of a system of subparallel fractures allows to approximate the actual rock anisotropy by a horizontal transverse isotropy model. The dataset was treated by different approaches, including simple cosine fit, inversion of average anisotropy parameters using a Monte-Carlo approach, isotropic and anisotropic tomography inversion. All of the above confirm the directions of fast and slow velocities (30°N and 120°N respectively) and an anisotropy of about 10%. Common measurements of seismic and resistivity data at different periods of the year will have the potential to determine quantitatively the fracture density and the free water content in this karst massif.

  5. Primordial anisotropies in gauged hybrid inflation

    Science.gov (United States)

    Akbar Abolhasani, Ali; Emami, Razieh; Firouzjahi, Hassan

    2014-05-01

    We study primordial anisotropies generated in the model of gauged hybrid inflation in which the complex waterfall field is charged under a U(1)gauge field. Primordial anisotropies are generated either actively during inflation or from inhomogeneities modulating the surface of end of inflation during waterfall transition. We present a consistent δN mechanism to calculate the anisotropic power spectrum and bispectrum. We show that the primordial anisotropies generated at the surface of end of inflation do not depend on the number of e-folds and therefore do not produce dangerously large anisotropies associated with the IR modes. Furthermore, one can find the parameter space that the anisotropies generated from the surface of end of inflation cancel the anisotropies generated during inflation, therefore relaxing the constrains on model parameters imposed from IR anisotropies. We also show that the gauge field fluctuations induce a red-tilted power spectrum so the averaged power spectrum from the gauge field can change the total power spectrum from blue to red. Therefore, hybrid inflation, once gauged under a U(1) field, can be consistent with the cosmological observations.

  6. Primordial anisotropies in gauged hybrid inflation

    International Nuclear Information System (INIS)

    Abolhasani, Ali Akbar; Emami, Razieh; Firouzjahi, Hassan

    2014-01-01

    We study primordial anisotropies generated in the model of gauged hybrid inflation in which the complex waterfall field is charged under a U(1)gauge field. Primordial anisotropies are generated either actively during inflation or from inhomogeneities modulating the surface of end of inflation during waterfall transition. We present a consistent δN mechanism to calculate the anisotropic power spectrum and bispectrum. We show that the primordial anisotropies generated at the surface of end of inflation do not depend on the number of e-folds and therefore do not produce dangerously large anisotropies associated with the IR modes. Furthermore, one can find the parameter space that the anisotropies generated from the surface of end of inflation cancel the anisotropies generated during inflation, therefore relaxing the constrains on model parameters imposed from IR anisotropies. We also show that the gauge field fluctuations induce a red-tilted power spectrum so the averaged power spectrum from the gauge field can change the total power spectrum from blue to red. Therefore, hybrid inflation, once gauged under a U(1) field, can be consistent with the cosmological observations

  7. Spin reorientation and magnetic anisotropy in Y2Co17-xCr x (x 1.17-3.0) compounds

    International Nuclear Information System (INIS)

    Fuquan, B.; Tegus, O.; Dagula, W.; Brueck, E.; Boer, F.R. de; Buschow, K.H.J.

    2005-01-01

    Spin reorientation transitions and magnetic anisotropy in Y 2 Co 17-x Cr x (x = 1.17-3.0) compounds have been investigated by means of X-ray diffraction and magnetization measurements. The powder X-ray diffraction patterns show that most samples crystallize as a single phase with the rhombohedral Th 2 Zn 17 -type structure. However, in the compound Y 2 Co 14 Cr 3 the Th 2 Zn 17 phase coexist with the hexagonal Th 2 Ni 17 -type phase. The lattice parameters a and c hardly change and the unit cell volume V increases slightly with increasing Cr content. The X-ray diffraction patterns of the aligned powder of the samples have confirmed that at room temperature the compound with x = 1.17 has planar anisotropy, but the compounds with x = 1.76, 2.34 and 3.00 have uniaxial anisotropy. Spin reorientation phenomena occur in all of the compounds. With increasing Cr content, the Curie temperature, the spin reorientation temperature, the spontaneous magnetization, and the anisotropy constant K 2 of the Y 2 Co 17-x Cr x (x = 1.17-3.0) compounds decrease strongly while the anisotropy constant K 1 increases in the range of x from 1.17 to 2.34 and then decreases in the range of x from 2.34 to 3.00

  8. Crustal anisotropy from Moho converted Ps wave splitting and geodynamic implications in Northeastern margin of Tibetan Plateau

    Science.gov (United States)

    Xie, Z.; Wu, Q.; Zhang, R.

    2017-12-01

    Collision between Indian and Eurasian result in intense deformation and crustal shortening in the Tibetan Plateau. NE margin of Tibetan Plateau experienced complex deformation between Qilian orogen and its adjacent blocks, Alxa Block in the north and Ordos Block in the east. We focus on if there any evidences exist in the NE margin of Tibetan Plateau, which can support crustal channel flow model. China Earthquake Administration had deployed temporary seismic array which is called ChinaArray Phase Ⅱ, dense seismic stations covered NE margin of Tibetan Plateau. Seismic data recorded by 81 seismic stations is applied in this research. We calculated receiver functions with time-domain deconvolution. We selected RFs which have clear Ps phase both in radial and transverse components to measure Ps splitting owing to crustal anisotropy, and 130 pairs of anisotropy parameters of 51 seismic stations were obtained. We would like to discuss about dynamic mechanism of this area using crustal anisotropy associated with the result of SKS-splitting and surface constrains like GPS velocity. The result can be summarized as follows. The large scale of delay time imply that the crustal anisotropy mainly derives from middle to lower crust rather than upper crust. In the southeastern part of the research area, crustal anisotropy is well agree with the result computed form SKS-splitting and GPS velocity directions trending NWW-SEE or E-W direction. This result imply a vertically coherent deformation in the area as the directions of crustal anisotropy trend to be perpendicular to the direction of normal stress. In the middle and north part of the research area, the fast polarization direction of crustal anisotropy is NEE-SWW or E-W direction, parallels with direction of GPS velocity, but differ to the direction of the result of SKS-splitting. This result may imply that decoupled deformation in this area associated with middle to lower crustal flow.

  9. Application of uniaxial confining-core clamp with hydrous pyrolysis in petrophysical and geochemical studies of source rocks at various thermal maturities

    Science.gov (United States)

    Lewan, Michael D.; Birdwell, Justin E.; Baez, Luis; Beeney, Ken; Sonnenberg, Steve

    2013-01-01

    Understanding changes in petrophysical and geochemical parameters during source rock thermal maturation is a critical component in evaluating source-rock petroleum accumulations. Natural core data are preferred, but obtaining cores that represent the same facies of a source rock at different thermal maturities is seldom possible. An alternative approach is to induce thermal maturity changes by laboratory pyrolysis on aliquots of a source-rock sample of a given facies of interest. Hydrous pyrolysis is an effective way to induce thermal maturity on source-rock cores and provide expelled oils that are similar in composition to natural crude oils. However, net-volume increases during bitumen and oil generation result in expanded cores due to opening of bedding-plane partings. Although meaningful geochemical measurements on expanded, recovered cores are possible, the utility of the core for measuring petrophysical properties relevant to natural subsurface cores is not suitable. This problem created during hydrous pyrolysis is alleviated by using a stainless steel uniaxial confinement clamp on rock cores cut perpendicular to bedding fabric. The clamp prevents expansion just as overburden does during natural petroleum formation in the subsurface. As a result, intact cores can be recovered at various thermal maturities for the measurement of petrophysical properties as well as for geochemical analyses. This approach has been applied to 1.7-inch diameter cores taken perpendicular to the bedding fabric of a 2.3- to 2.4-inch thick slab of Mahogany oil shale from the Eocene Green River Formation. Cores were subjected to hydrous pyrolysis at 360 °C for 72 h, which represents near maximum oil generation. One core was heated unconfined and the other was heated in the uniaxial confinement clamp. The unconfined core developed open tensile fractures parallel to the bedding fabric that result in a 38 % vertical expansion of the core. These open fractures did not occur in the

  10. Electric field dependence of the spin relaxation anisotropy in (111) GaAs/AlGaAs quantum wells

    International Nuclear Information System (INIS)

    Balocchi, A; Amand, T; Renucci, P; Duong, Q H; Marie, X; Wang, G; Liu, B L

    2013-01-01

    Time-resolved optical spectroscopy experiments in (111)-oriented GaAs/AlGaAs quantum wells (QWs) show a strong electric field dependence of the conduction electron spin relaxation anisotropy. This results from the interplay between the Dresselhaus and Rashba spin splitting in this system with C 3v symmetry. By varying the electric field applied perpendicular to the QW plane from 20 to 50 kV cm −1 the anisotropy of the spin relaxation time parallel (τ s ∥ ) and perpendicular (τ s ⊥ ) to the growth axis can be first canceled and eventually inversed with respect to the one usually observed in III–V zinc-blende QW (τ s ⊥ = 2τ s ∥ ). This dependence stems from the nonlinear contributions of the k-dependent conduction band spin splitting terms which begin to play the dominant spin relaxing role while the linear Dresselhaus terms are compensated by the Rashba ones through the applied bias. A spin density matrix model for the conduction band spin splitting including both linear and cubic terms of the Dresselhaus Hamiltonian is used which allows a quantitative description of the measured electric field dependence of the spin relaxation anisotropy. The existence of an isotropic point where the spin relaxation tensor reduces to a scalar is predicted and confirmed experimentally. The spin splitting compensation electric field and collision processes type in the QW can be likewise directly extracted from the model without complementary measurements. (paper)

  11. A perturbative DFT approach for magnetic anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Khoo, Khoong Hong; Laskowski, Robert, E-mail: rolask@ihpc.a-star.edu.sg

    2017-04-15

    We develop a perturbative formalism for computing magnetocrystalline anisotropy within density functional theory and the magnetic force theorem. Instead of computing eigenvalues of the spin–orbit Hamiltonian for selected spin polarizations, as in the conventional “force theorem” approach, we show that the effect can be cast into a redefined form of the spin–orbit operator. This allows to separate the large eigenvalue shift due to spin-orbit interaction common for both polarizations from the much smaller magnetic anisotropy splitting. As a consequence the anisotropy splitting may by considered as a perturbation.

  12. Magnetization Switching of a Co /Pt Multilayered Perpendicular Nanomagnet Assisted by a Microwave Field with Time-Varying Frequency

    Science.gov (United States)

    Suto, Hirofumi; Kanao, Taro; Nagasawa, Tazumi; Mizushima, Koichi; Sato, Rie

    2018-05-01

    Microwave-assisted magnetization switching (MAS) is attracting attention as a method for reversing nanomagnets with a high magnetic anisotropy by using a small-amplitude magnetic field. We experimentally study MAS of a perpendicularly magnetized nanomagnet by applying a microwave magnetic field with a time-varying frequency. Because the microwave field frequency can follow the nonlinear decrease of the resonance frequency, larger magnetization excitation than that in a constant-frequency microwave field is induced, which enhances the MAS effect. The switching field decreases almost linearly as the start value of the time-varying microwave field frequency increases, and it becomes smaller than the minimum switching field in a constant-frequency microwave field. To obtain this enhancement of the MAS effect, the end value of the time-varying microwave field frequency needs to be almost the same as or lower than the critical frequency for MAS in a constant-frequency microwave field. In addition, the frequency change typically needs to take 1 ns or longer to make the rate of change slow enough for the magnetization to follow the frequency change. This switching behavior is qualitatively explained by the theory based on the macrospin model.

  13. Electric-field assisted switching of magnetization in perpendicularly magnetized (Ga,Mn)As films at high temperatures

    Science.gov (United States)

    Wang, Hailong; Ma, Jialin; Yu, Xueze; Yu, Zhifeng; Zhao, Jianhua

    2017-01-01

    The electric-field effects on the magnetism in perpendicularly magnetized (Ga,Mn)As films at high temperatures have been investigated. An electric-field as high as 0.6 V nm-1 is applied by utilizing a solid-state dielectric Al2O3 film as a gate insulator. The coercive field, saturation magnetization and magnetic anisotropy have been clearly changed by the gate electric-field, which are detected via the anomalous Hall effect. In terms of the Curie temperature, a variation of about 3 K is observed as determined by the temperature derivative of the sheet resistance. In addition, electrical switching of the magnetization assisted by a fixed external magnetic field at 120 K is demonstrated, employing the gate-controlled coercive field. The above experimental results have been attributed to the gate voltage modulation of the hole density in (Ga,Mn)As films, since the ferromagnetism in (Ga,Mn)As is carrier-mediated. The limited modulation magnitude of magnetism is found to result from the strong charge screening effect introduced by the high hole concentration up to 1.10  ×  1021 cm-3, while the variation of the hole density is only about 1.16  ×  1020 cm-3.

  14. Effect of spin structure transition in IrMn on the CoPd/IrMn perpendicular exchange biased system

    Energy Technology Data Exchange (ETDEWEB)

    Janjua, Muhammad Bilal; Guentherodt, Gernot [II. Physikalisches Institut A, RWTH Aachen University, Aachen (Germany)

    2011-07-01

    The exchange bias (EB) phenomenon is studied in MBE grown Pd(10 nm)/CoPd(x=8,16,30 nm)/IrMn(15 nm)/Pd(4 nm) samples, which exhibit a perpendicular anisotropy of Co22Pd78. These samples are field cooled along the out-of-plane direction and hysteresis loops are measured along both the out-of-plane and in-plane directions. It is observed that there is a transition temperature where the out-of-plane EB becomes greater than the in-plane EB. This behavior of EB is an evidence of the change in the spin structure of the given system, which is also revealed by the magnetization versus temperature measurements of the exchange biased and of the sole IrMn samples. It is found that with increasing temperature there is a spin structure transition in Ir25Mn75 (15nm) related to the 2Q to 3Q transition in the bulk, which is responsible for the increase in out-of-plane EB. A vertical shift in the hysteresis loop is also observed in these exchange biased samples at low temperatures (T<50 K).

  15. 2D magnetization of grain-oriented 3%-Si steel under uniaxial stress

    International Nuclear Information System (INIS)

    Permiakov, V.; Dupre, L.; Pulnikov, A.; Melkebeek, J.

    2005-01-01

    Magnetization in electrical steels is strongly affected by mechanical stress. The stress dependence of magnetic properties of non-oriented steels has been studied at one- and two-dimensional magnetization. This paper deals with the stress effect on one- and two-dimensional magnetization in grain-oriented 3%-Si steel. The special magnetic measurements system is applied to combine uniaxial stress and 2D magnetic measurements. The uniaxial stress ranges from 10 MPa compressive stress to 100 MPa tensile stress. A domain theory is a suitable tool for prediction and a physical explanation of stress dependency in grain-oriented steel

  16. The statitistical evaluation of the uniaxial compressive strength of the Ruskov andesite

    Directory of Open Access Journals (Sweden)

    Krepelka František

    2002-03-01

    Full Text Available The selection of a suitable model of the statistical distribution of the uniaxial compressive strength is discussed in the paper. The uniaxial compressive strength was studied on 180 specimens of the Ruskov andesite. The rate of loading was 1MPa.s-1. The experimental specimens had a prismatic form with a square base; the slightness ratio of specimens was 2:1. Three sets of specimens with a different length of the base edge were studied, namely 50, 30 and 10 mm. The result of the measurement were three sets with 60 values of the uniaxial compressive strength. The basic statistical parameters: the sample mean, the sample standard deviation, the variational interval, the minimum and maximum value, the sample obliqueness coefficient and the sharpness coefficient were evaluated for each collection. Two types of the distribution which can be joined with the real physical fundamentals of the desintegration of rocks ( the normal and the Weibull distribution were tested. The two-parametric Weibull distribution was tested. The basic characteristics of both distributions were evaluated for each set and the accordance of the model distribution with an experimental distribution was tested. The ÷2-test was used for testing. The two-parametric Weibull distribution was selected following the comparison of the test results of both model distributions as a suitable distribution model for the characterization of uniaxial compressive strength of the Ruskov andesite. The two-parametric Weibull distribution showed better results of the goodness-of-fit test. The normal distribution was suitable for two sets; one of the sets showed a negative result of the goodness-of-fit testing. At the uniaxial compressive strength of the Ruskov andesite, a scale effect was registered : the mean value of uniaxial compressive strength decreases with increasing the specimen base edge. This is another argument for using the Weibull distribution as a suitable statistical model of the

  17. The impact of uniaxial stress on subband structure and mobility of strain Si NMOSFETs

    International Nuclear Information System (INIS)

    Chang, S.T.; Liao, S.H.; Lin, C.-Y.

    2008-01-01

    An effect of stress distortion on the conduction band structure was derived by k.p method considering a second order perturbation. From k.p conduction band calculations, stress-induced band edge split and the change of effective mass are quantitatively evaluated. The physical reasons of warped subband structure and abnormal mobility enhancement by uniaxial stress are investigated. Variation rates of experimental electron mobility in the silicon n-channel metal-oxide-semiconductor field-effect-transistors under a [110] uniaxial stress as a function of channel direction is theoretically studied

  18. Experimental study on uniaxial ratcheting deformation and failure behavior of 304 stainless steel

    International Nuclear Information System (INIS)

    Yang Xianjie; Gao Qing; Cai Lixun; Liu Yujie

    2004-01-01

    In the paper, the tests of cyclic strain ratcheting and low cycle fatigue for 304 stainless steel under uniaxial cyclic straining were carried out to systematically explore the deformation and failure behavior of the material. The experimental study shows that the cyclic strain ratcheting deformation behavior of the material is different from either the uniaxial monotonic tensile one or the cyclic deformation one under the symmetrical cyclic straining with the same strain amplitude, and the strain ratcheting deformation and failure behaviors depend on both the plastic strain amplitude and the strain increment at the cyclic maximum strain. Some significant results were observed

  19. Secondary School Mathematics, Chapter 13, Perpendiculars and Parallels (I), Chapter 14, Similarity. Student's Text.

    Science.gov (United States)

    Stanford Univ., CA. School Mathematics Study Group.

    The first chapter of the seventh unit in this SMSG series discusses perpendiculars and parallels; topics covered include the relationship between parallelism and perpendicularity, rectangles, transversals, parallelograms, general triangles, and measurement of the circumference of the earth. The second chapter, on similarity, discusses scale…

  20. Topological spin-hedgehog crystals of a chiral magnet as engineered with magnetic anisotropy

    Science.gov (United States)

    Kanazawa, N.; White, J. S.; Rønnow, H. M.; Dewhurst, C. D.; Morikawa, D.; Shibata, K.; Arima, T.; Kagawa, F.; Tsukazaki, A.; Kozuka, Y.; Ichikawa, M.; Kawasaki, M.; Tokura, Y.

    2017-12-01

    We report the engineering of spin-hedgehog crystals in thin films of the chiral magnet MnGe by tailoring the magnetic anisotropy. As evidenced by neutron scattering on films with different thicknesses and by varying a magnetic field, we can realize continuously deformable spin-hedgehog crystals, each of which is described as a superposition state of a different set of three spin spirals (a triple-q state). The directions of the three propagation vectors q vary systematically, gathering from the three orthogonal 〈100 〉 directions towards the film normal as the strength of the uniaxial magnetic anisotropy and/or the magnetic field applied along the film normal increase. The formation of triple-q states coincides with the onset of topological Hall signals, that are ascribed to skew scattering by an emergent magnetic field originating in the nontrivial topology of spin hedgehogs. These findings highlight how nanoengineering of chiral magnets makes possible the rational design of unique topological spin textures.